WO2017142784A1 - Improved electrical feed through holes for photovoltaic modules - Google Patents

Abstract

Stiffening elements are disclosed to improve the survivability of the glass substrate in photovoltaic modules when subjected to impact damage. There are two elements that can be used separately or together in a PV module - a first stiffening element composed of a plug that fits in the feed through hole and a second stiffening element composed of a plate mounted to the back of the module, between the junction box and the back glass.

Description

IMPROVED ELECTRICAL FEED THROUGH HOLES FOR PHOTOVOLTAIC MODULES

[0001] This application claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application Serial No. 62/295,839 filed on February 16, 2016, the content of which is relied upon and incorporated herein by reference in its entirety.

BACKGROUND

Field

[0002] Embodiments relate to improved designs for feed through holes in photovoltaic (PV) modules.

Technical Background

[0003] Photovoltaic modules are used to convert sunlight into electricity. Two major types used or in development today are wafered modules using multiple silicon wafers connected together (such as shown in Figs. 1A and IB) and thin film modules using one of a variety of inorganic then film materials, such as cadmium telluride (CdTe), copper indium gallium di-selenide (CIGS) or thin film (amorphous and micro crystalline) silicon (such as shown in Fig. 1C). Typical packages for PV modules have a glass substrate, such as a soda lime glass, back contact, the semiconductor layer or layers, a front contact or transparent contact layer (TCO), and a protective cover layer, such as a glass substrate. Additionally, almost all packages have electrical contacts that exit the package. The place where the contacts emerge from the package provides a point of entry for moisture as well as a possible structural weakness in the package design. Because of the continuing drive to make PV technology competitive with existing power production methods, e.g., hydro, coal, nuclear, wind, etc., in the power generation industry, any opportunities to improve PV device design and/or efficiency must be exploited. Clearly, there is still an unmet need to find PV module designs that provide improved contact output while retaining strength and minimizing moisture ingress. BRIEF SUMMARY

[0004] A first aspect is the addition of stiffening elements to the module to improve the survivability of the module during a hail impact. There are two elements that can be used separately or together in a PV module. The first stiffening element is a plug that fits in the feed through hole and is slightly smaller than the feed through hole and the same thickness of the glass with the feed through hole. An ideal plug material is the glass itself. Figs. 4A-B illustrates a soda lime glass plug in a module with a tempered soda lime back glass and a thin glass plug in a module with an untempered specialty glass. Both of these plugs provide additional support to the thin front glass and reduce the probability that the front glass fractures during a hail impact. For example, for a 19 mm diameter feed through hole, the plugs are necessary when the front glass thickness is 1.5mm or less and add additional protection for any untempered glass up to standard soda lime glass thicknesses. These plugs do not help to improve the resistance to fracture of the back glass during hail impact.

[0005] A second aspect comprises a second stiffening element comprising a stiffening plate mounted to the back of the module, between the junction box and the back glass as shown in Figs. 5A-B. This plate locally increases the stiffness of the module and shifts the location of the feed through hole to the center of the stack where there are reduced bending stresses. This plate reduces the risk of hail induced fracture from the edge 180 of the feed through hole 122. This stiffening plate does not provide support for the front glass over the feed through hole. Thus it makes sense to use both methods to improve the hail performance at the feed through hole. This stiffening plate is not necessary with a tempered soda lime back glass of 3.2 mm to 4.0 mm, thus it is only shown with the two thin sheets of specialty glass in Fig. 5. The stiffening plate can be used with or without the thin glass plug as shown by the two drawings in Fig. 5.

[0006] In another aspect of the photovoltaic modules comprising the glasses listed above, the photovoltaic module further comprises a hermetic/watertight seal along the edge and between the first and second outer protective layers to form a hermetically sealed cavity comprising the at least one crystalline silicon solar cell wafer. [0007] In another aspect of the photovoltaic modules comprise at least one glass sheet has a thickness of 1.8 mm or less. In another aspect of the photovoltaic modules comprise at least one of the glass sheets has a thickness of 0.5 mm or less. In some embodiments, the glass sheet having a thickness of 0.5 mm or less is capable of being processed under roll-to- roll conditions. In another aspect of the photovoltaic modules comprise a Na-containing structural glass sheet having a thickness of greater than 1.5 mm.

[0008] These and other aspects, advantages, and salient features will become apparent from the following detailed description, the accompanying drawings, and the appended claims.

FIGURES

[0009] Figs. 1A-1C shows cross-sectional illustrations of traditional (prior art) PV modules. Fig. 1A shows a c-Si PV module with single sheet of tempered soda lime glass and a polymeric backsheet, Fig. IB shows a c-Si PV module composes of two soda lime glass sheets, and Fig. 1C provides an example of a thin film PV module comprises of two soda lime glass sheets.

[0010] Figs. 2A-2C show cross-sectional illustrations of c-Si PV modules utilizing two sheets (Fig. 2A), one sheet on front (Fig. 2B), and one sheet on back (Fig. 2C) of specialty thin glass. Fig. 2D is an alternate embodiment of a thin film PV module comprising two specialty thin glass sheets

[0011] Figs. 3A and 3B are tables describing fracture rates at feed through hole with varying glass thicknesses (Fig. 3A) and with varying feed through hole sizes with 0.7 mm front glass and 4.0 mm tempered soda lime back glass (Fig. 3B).

[0012] Figs. 4A and 4B are illustrations of a glass plug in a module with a tempered soda lime back glass (Fig. 4A) and a thin untempered specialty glass (Fig. 4B).

[0013] Figs. 5A and 5B are illustrations of embodiments of PV modules with stiffening plates in the module. [0014] Fig. 6 compares a detailed views of the glass substrate with a feed through hole (Fig. 6A) and feed through plus plug (Fig. 6B).

[0015] Figs. 7A-7F are alternative design embodiments for the feed through hole and plug design.

[0016] Fig. 8 is a detailed drawing of the stiffening plate situated over a feed through hole (dotted lines) with two holes for the electrical leads.

[0017] Fig. 9 is a detailed drawing of the stiffening plate situated over 2 feed through holes (dotted lines) with two holes for electrical leads.

[0018] Fig. 10 is a detailed drawing of the stiffening plate situated over single large feed through hole (dotted lines) with two holes (Fig. 10A) or single larger hole (Fig. 10B) for electrical leads.

[0019] Fig. 11 shows an alternative embodiment composed of a PV Module with two sheets of thin specialty glass having a junction box with an integrated stiffening plate and a thin glass plug in the feed through hole.

[0020] Fig. 12 is an alternative embodiment composed of a PV Module with two sheets of thin specialty glass having a junction box with an integrated stiffening plate and feed through hole plug.

[0021] Fig. 13 is an alternative embodiment composed of a PV Module with one sheet of thin specialty glass and a stiffening plate integrated with a feed through hole.

[0022] Fig. 14 is an alternative embodiment composed of a PV Module with two sheets of thin specialty glass, a junction box, with a thin glass plug and a stiffening plate completely inside the junction box.

[0023] Fig. 15 is an alternative embodiment composed of a PV Module with a feed through hole at the edge having a thin glass plug and a stiffening plate integrated into the junction box. [0024] Fig. 16 shows an embodiment composed of PV modules with an internal stiffening layer embedded in the encapsulant with two sheets of thin specialty. The internal stiffening layer needs to be non-conducting due to its proximity to the internal electrical leads 116. In some embodiments, a ceramic or glass fiber woven mat is a possible candidate.

[0025] Fig. 17 shows an alternative embodiment of the PV module wherein the plug has an angled edge or wedge design to prevent it from being pushed out of the device or dislodged in an impact event. The junction box and potting material may be directly connected to the plug (as shown) or one or more additional stiffening plates may be included between the components or integrated into the junction box, similar to Figs. 5B, 11, and 12.

[0026] Figs. 18A and 18B describe the angles that are possible on the beveled edges of the plug.

DETAILED DESCRIPTION

[0027] In the following detailed description, numerous specific details may be set forth in order to provide a thorough understanding of embodiments of the invention. However, it will be clear to one skilled in the art when embodiments of the invention may be practiced without some or all of these specific details. In other instances, well-known features or processes may not be described in detail so as not to unnecessarily obscure the invention. In addition, like or identical reference numerals may be used to identify common or similar elements. Moreover, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, the present specification, including the definitions herein, will control.

[0028] Although other methods and can be used in the practice or testing of the invention, certain suitable methods and materials are described herein. [0029] Disclosed are materials, compounds, compositions, and components that can be used for, can be used in conjunction with, can be used in preparation for, or are embodiments of the disclosed method and compositions. These and other materials are disclosed herein, and it is understood that when combinations, subsets, interactions, groups, etc. of these materials are disclosed that while specific reference of each various individual and collective combinations and permutation of these compounds may not be explicitly disclosed, each is specifically contemplated and described herein.

[0030] Thus, if a class of substituents A, B, and C are disclosed as well as a class of substituents D, E, and F, and an example of a combination embodiment, A-D is disclosed, then each is individually and collectively contemplated. Thus, in this example, each of the combinations A-E, A-F, B-D, B-E, B-F, C-D, C-E, and C-F are specifically contemplated and should be considered disclosed from disclosure of A, B, and/or C; D, E, and/or F; and the example combination A-D. Likewise, any subset or combination of these is also specifically contemplated and disclosed. Thus, for example, the sub-group of A-E, B-F, and C-E are specifically contemplated and should be considered disclosed from disclosure of A, B, and/or C; D, E, and/or F; and the example combination A-D. This concept applies to all aspects of this disclosure including, but not limited to any components of the compositions and steps in methods of making and using the disclosed compositions. Thus, if there are a variety of additional steps that can be performed it is understood that each of these additional steps can be performed with any specific embodiment or combination of embodiments of the disclosed methods, and that each such combination is specifically contemplated and should be considered disclosed.

[0031] Moreover, where a range of numerical values is recited herein, comprising upper and lower values, unless otherwise stated in specific circumstances, the range is intended to include the endpoints thereof, and all integers and fractions within the range. It is not intended that the scope of the invention be limited to the specific values recited when defining a range. Further, when an amount, concentration, or other value or parameter is given as a range, one or more preferred ranges or a list of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether such pairs are separately disclosed. Finally, when the term "about" is used in describing a value or an end-point of a range, the disclosure should be understood to include the specific value or end-point referred to.

[0032] As used herein, the term "about" means that amounts, sizes, formulations, parameters, and other quantities and characteristics are not and need not be exact, but may be approximate and/or larger or smaller, as desired, reflecting tolerances, conversion factors, rounding off, measurement error and the like, and other factors known to those of skill in the art. In general, an amount, size, formulation, parameter or other quantity or characteristic is "about" or "approximate" whether or not expressly stated to be such.

[0033] The term "or", as used herein, is inclusive; more specifically, the phrase "A or B" means "A, B, or both A and B". Exclusive "or" is designated herein by terms such as "either A or B" and "one of A or B", for example.

[0034] The indefinite articles "a" and "an" are employed to describe elements and components of the invention. The use of these articles means that one or at least one of these elements or components is present. Although these articles are conventionally employed to signify that the modified noun is a singular noun, as used herein the articles "a" and "an" also include the plural, unless otherwise stated in specific instances. Similarly, the definite article "the", as used herein, also signifies that the modified noun may be singular or plural, again unless otherwise stated in specific instances.

[0035] For the purposes of describing the embodiments, it is noted that reference herein to a variable being a "function" of a parameter or another variable is not intended to denote that the variable is exclusively a function of the listed parameter or variable. Rather, reference herein to a variable that is a "function" of a listed parameter is intended to be open ended such that the variable may be a function of a single parameter or a plurality of parameters.

[0036] It is noted that terms like "preferably," "commonly," and "typically," when utilized herein, are not utilized to limit the scope of the claimed invention or to imply that certain features are critical, essential, or even important to the structure or function of the claimed invention. Rather, these terms are merely intended to identify particular aspects of an embodiment of the present disclosure or to emphasize alternative or additional features that may or may not be utilized in a particular embodiment of the present disclosure.

[0037] It is noted that one or more of the claims may utilize the term "wherein" as a transitional phrase. For the purposes of defining the present invention, it is noted that this term is introduced in the claims as an open-ended transitional phrase that is used to introduce a recitation of a series of characteristics of the structure and should be interpreted in like manner as the more commonly used open-ended preamble term "comprising."

[0038] The terms "solar cell," "photovoltaic cell," "PV cell," "solar module," "photovoltaic module," "PV module," "solar device," "photovoltaic device," "PV device," or "device," as used herein, refer to any article that can convert light into electrical energy. Suitable solar cells include thin-film solar cells, such as CIGS, CdTe, CdS, amorphous or thin-film Si, dye- sensitized solar, etc. A solar cell assembly can comprise one or a plurality of solar cells. The plurality of solar cells can be electrically interconnected or arranged in a flat plane. In addition, the solar cell assembly can further comprise conductive pastes or electrical wirings deposited upon the solar cells.

[0039] As a result of the raw materials and/or equipment used to produce the glass composition of the present invention, certain impurities or components that are not intentionally added, can be present in the final glass composition. Such materials are present in the glass composition in minor amounts and are referred to herein as "tramp materials."

[0040] As used herein, a glass composition having 0 mol% of a compound is defined as meaning that the compound, molecule, or element was not purposefully added to the composition, but the composition may still comprise the compound, typically in tramp or trace amounts. Similarly, "iron-free," "alkali earth metal-free," "heavy metal-free" or the like are defined to mean that the compound, molecule, or element was not purposefully added to the composition, but the composition may still comprise iron, alkali earth metals, or heavy metals, etc., but in approximately tramp or trace amounts.

[0041] Most photovoltaic (PV) modules are required to pass design qualification and type approval requirements according to the International Electrochemical Commission standards, IEC-61215 (crystalline silicon modules) or IEC-61646 (thin film PV modules) prior to their commercialization. These requirements include the measurement of key performance metrics before and after a variety of exposures including damp heat, thermal cycling, humidity freeze, mechanical loading, hail impact, outdoor exposure, and robustness of terminations. Of interest for this invention is the hail impact test. This test involves impacting a module with 25 mm diameter ice balls at 23 m/s at 11 impact locations. Of these locations, 10 are clearly specified and the 11^th one is to be directed at any location the tester feels is particularly vulnerable to hail damage. Additionally the standard also lists a table of ice ball sizes and speeds up to 75 mm diameter and 39.5 m/s that can be used for qualification in special environments.

[0042] The hail performance of PV modules is largely determined by the glass used in the module. Typical PV modules use either 1 sheet of tempered soda lime glass that is 3.2- 4.0 mm thick or 2 sheets of soda lime glass 3.2-4.0 mm thick, one of which is tempered, and the other which may or may not be tempered. These two basic geometries are illustrated in Figs. 1A and IB with a c-Si configuration, but can also be used with thin film modules.

[0043] Continuing to look at Figs. 1A and IB, these conventional modules 100 are comprised of a sheet of tempered soda lime glass 110 on the front having an outside-facing (or sun) side and an inside-facing (or device) side. In the case of a c-Si PV module, the device side of the glass is adhered to an encapsulant layer 112. The encapsulant layer 112 contains the c-Si cells 114 and electrical leads 116. Placement of these items within the encapsulant 112 is achieved by using two encapsulant sheets on either side of these items. In Fig. la, a polymeric backsheet 118 is then placed on the back and this stack is placed in a laminator, allowing the encapsulant sheets to flow and adhere to the various layers. Small slits in the backsheet 118 allow the electrical leads 116 to exit the laminate stack. In the case of a dual glass module (Fig. IB), the polymeric backsheet is replaced with another tempered soda lime glass sheet 120. A hole cut 122 into the glass sheet 120 on the back allows the electrical leads 116 to exit the device. After the glass backsheet 120 or polymer back sheet 118 is in place, a frame 124 with a gasket 126 is added, and a junction box 128 is bonded to the back of the module with an adhesive in the location where the electrical leads 116 exit the laminate stack. In some embodiments, the junction box 128 comprises a polymer or resin, such as a nylon comprising glass fibers, polyphenylene oxide, polyvinylchloride, etc. The junction box is commonly filled or partially filled with a potting material 130, such as an epoxy, polyurethane, silicone, or other resin. In some cases, such as that shown in Fig. IB, the potting material 130 may fill part of the hole 122 in the glass back sheet.

[0044] Common materials used for the PV components in a c-Si PV device as described above include encapsulants, such as EVA, PVB, ionomer, silicone; frame: metals, such as extruded aluminum, steel, polymers, such as polyvinyl chloride; gasket: silicone, urethane; junction box adhesive: silicone; j-box potting: epoxy, polyurethane, silicone, or other resin.

[0045] Thin film PV devices are somewhat similar in structure, having front and rear sheets of glass HOC and 102C, acrylic or other material, but the interior components are generally a sandwich structure comprising, from the front face to the bottom face, a transparent conductive oxide 132, at least one photovoltaic layers 134, and another conductive layer 136 that may be transparent (Fig. 1C). The film layers 132, 134, 136 can be directly adhered to the front and/or back glass, making the entire design very thin.

[0046] Thin specialty glasses are of interest for use in PV modules due to their increased transmission, improved durability, and ability to reduce and eliminate degradation due to an applied negative electrical bias. Incorporating thin specialty glass into a glass-glass package enables capturing of the listed benefits, plus significantly reduced moisture ingress compared to modules with polymer back sheets. Figs. 2A-2D illustrate four designs utilizing thin specialty glass. The device in Fig. 2A contains two sheets of thin specialty glass 210, 220. The second device (Fig. 2B) contains one sheet of thin specialty glass 210 on the front with tempered soda lime glass on the back 120. The third (Fig. 2C) contains one sheet of thin specialty glass 220 on the back with tempered soda lime glass on the front 110. Note that in some embodiments, these three designs could also comprise thin soda lime glass instead of a thin specialty glass. The fourth, Fig. 2D, is similar to the device in Fig. 1C, but includes at least one thin specialty glass as the front glass sheet 210 or as the back glass sheet 220.

[0047] In many applications, the thin glass is untempered because of cost and/or difficulties related to tempering the thin sheets. Additionally, some specialty glasses of interest for this application have a lower coefficient of thermal expansion and a higher strain point, further increasing the difficulty to temper the glass. It is this loss of tempering with the decreased glass thickness in the designs in Figs. 2A-D that make the thin-glass containing PV modules more susceptible to hail impact damage and less likely to pass the hail portion of the IEC qualification requirements. This increased hail damage susceptibility is particularly concerning at the feed through hole 122. Hail impact to the module at the feed through hole 122 with two sheets of thin untempered specialty glass will result in high stresses in the front sheet 210 due to it being pushed through the feed through hole 122 in the back sheet 220 as it is unsupported. Additionally the thin back sheet of glass 220 is also at an increased risk of hail impact damage due to the machined edge 180 of the feed through hole 122, reducing its strength, in addition to the overall increase in stress due to the glass thickness decrease. In the case when one sheet of thin untempered specialty glass sheet 210 used with a tempered soda lime on the back 120, generally only the front glass 210 is at a particularly high risk for fracture since the thick tempered soda lime glass 120 has adequate protection itself.

[0048] A first aspect is a PV module comprising thin glass front and/or back sheets along with additional stiffening elements in the module to improve the survivability of the module during a hail impact. One embodiment described herein is a stiffening element comprising a plug 440 that fits at least partially in the feed through hole. Reference to 440 is interchangeable with references to 440A and 440B herein. The plug 440 comprises a generally rigid structure that fills the feed through hole 122 and provides sufficient support or structural integrity to the front glass that it isn't damaged or destroyed under commercial or industry design qualifications or standards or field tests.

[0049] The plug 440 geometry may essentially be any geometry that sufficiently fills the feed through hole and provides the necessary structural support. Generally, the plug 440 is designed to mirror the shape of the feed through hole but is dimensionally smaller leaving a small gap 445 to allow for wire egress. The edge 180 of the feed through hole 122 may have any number of shapes. For example, the feed through hole edge 180 may be flat, flat polished, rounded, bullnosed, half bullnosed, beveled, chamfered, cove-edged, etc. Similarly, the plug 440 may have any number of shapes that in some embodiments, may be identical to the feed through hole edge 180. Alternatively, the plug edge 1810 and/or the feed through hole edge 180 may be designed to improve structural strength or integrity. In some embodiments, the edge 180, 1810 on one or both of the feed through hole 122 and/or the plug 440, respectively, may be beveled, angled, or shaped in such a way that the glass back sheet 120, 220 provides structural support to the plug 440 and/or vice versa. For example, as shown in Fig. 17, the plug 440 may have a beveled edge 1810 wherein the interior surface of the plug 440 is dimensionally larger in diameter than the exterior surface. Complementary, the back sheet is reverse beveled so the feed through hole edge 180 provides support for the plug 440 and prevent the plug 440 from being pushed out. In some embodiments, where the plug 440 has a beveled shape, such as that shown in Fig. 17, the bevel angle a has a maximum angle of 60° and a minimum angle of that required to bridge the gap 445 (on one side) between the plug and the substrate (solid line, Fig. 18B). The minimum angle a may be approximately arctan (gap/substrate thickness). For reference, as shown in Fig. 18A, a straight plug has a 0° angle (dotted lines showing angles). Angles a larger than 60° may lead to weaknesses and unnecessary grinding. In some embodiments, the minimum angle a is in the range from approximately arctan (gap/substrate thickness) to approximately 2 [arctan(gap/substrate thickness]. For example, if the gap 445 is 1 mm and the substrate is 3.2 mm thick, the angle a of the bevel of the plug is from about 30 to 40°. [0050] Referring again to Fig. 18B, the plug 440 may also have a negative angle β bevel to improve adhesion or bonding of the back sheet to the plug (dashed lines). As above, the angle β of the negative bevel can be approximated by arctan(gap/substrate thickness) or 2 [arctan(gap/substrate thickness]. In some embodiments, the angle β bevel is from -60° or less, -40° or less, or -30° or less. In such embodiments, the back sheet 220 alone would not retain the plug, but the use of adhesive, glass frit or the like may be used to bond the plug to the back sheet and the added surface area can improve the adhesion properties.

[0051] In some embodiments, the plug 440 is similar or identical to the back glass sheet 120, 220 in thickness. In some embodiments, the plug 440 is thicker than the back glass sheet and the additional thickness is retained on the inside of the device, the outside of the device or both. In some embodiments, the plug is thinner than the back glass sheet. In such embodiments, the plug 440 may be retained anywhere within the feed through hole 122, such as near the inside edge of the feed through hole 122, the outside edge, or anywhere in between.

[0052] The feed through hole 122 plug 440 properties can play a significant role in how effective the plug 440 is at supporting the front glass substrate and/or the back glass substrate. In some embodiments, the plug 440 has a CTE from 0 ppm/°C to about 100 ppm/°C from 25°C to 300°C. In some embodiments, the CTE of plug 440 is from 0 ppm/°C to about 30 ppm/°C from 25°C to 300°C. In some embodiments, the CTE of the plug 440 is substantially similar to the CTE of the back sheet. In such embodiments, the plug 440 CTE may be within ±10 ppm/°C, ±8 ppm/°C, ±5 ppm/°C, or ±2 ppm/°C of the CTE of the back glass. In some embodiments, the plug 440 has an elastic modulus of from about 1 GPa to about 220 Gpa, or alternatively, about 10 GPa to about 220 Gpa, or about 60 GPa to about 80 Gpa.

[0053] The plug 440 may comprise any material that is compatible with the materials in the photovoltaic module and provides the requisite properties. The plug 440, in some embodiments, may comprise glass, ceramic, glass ceramic, metal, polymer, or combinations thereof. Because of the fact that electrical leads 116 are passing near the plug 440, it is generally not made of conductive materials or if it is, such materials are coated, or used in combination with, non-conductive materials. In some embodiments, the plug 440 comprises a glass material. In some embodiments, the glass of the plug 440 is compositionally similar to or identical to, the composition of the glass back sheet. This is advantageous in that the plug 440 and glass back sheet 120, 220 then have substantially equivalent physical properties, such as CTE, hardness, etc. In some embodiments, it is advantageous for the plug 440 to apply a compressive stress to the feed through hole. In such embodiments, the plug 440 may comprise a glass composition with a higher CTE than the CTE of the glass composition comprising the glass back sheet.

[0054] In some embodiments, the plug 440 material is a glass of similar thickness and composition as the back glass sheet. In embodiments, plug 400 substantially fills feed through hole 122 while allowing passage of electrical leads 116. Figs. 4A and 4B illustrate a soda lime glass plug 440A in a module with a tempered soda lime back glass (Fig. 4A) and a thin glass plug 440B in a module with an untempered specialty glass (Fig. 4B). In both cases shown, the junction box 128 is adhered directly behind the feed through hole 122 with optional potting material 130 between. Both of these plugs 440A, 440B provide additional support to the thin front glass sheet 210 and reduce the probability that the front glass fractures during a hail impact. For a 19 mm diameter feed through hole 122, the plugs are necessary when the front glass thickness is 1.5 mm or less and add additional protection for any untempered glass up to standard soda lime glass thicknesses.

[0055] Feed through hole 122 diameters can vary from 6 mm to 50 mm. Common feed through hole 122 diameters are 8 mm and 20 mm. In some embodiments, the diameter of the plug 440 is slightly smaller than the feed through hole 122. A diameter of plug 440 may be about 1 mm smaller than the feed through hole 122, providing a 0.5 mm gap 445 on each side of the plug 400, therefore allow adequate space for the electrical leads 116 to fit between the edges 180, 1810 of the feed through hole 122 and plug 440, respectively. The gap 445 between the feed through hole 122 and the plug 440 could be increased to about 3 mm if additional space is needed for the electrical leads 116, but this could degrade the hail performance. In some embodiments, the gap 445 may not be even across the entire hole 122 such that it provides larger gaps 445 where the electrical leads 116 go through and narrower gaps 445 in other regions. For example, the gap 445 may be up to about 3 mm where the electrical leads go through, but 0.25 mm or 0.5 mm everywhere else. In some embodiments, the gap 445 between the plug 440 and the feed through hole 122 for an approximately evenly centered plug 440 (e.g., the gap 445 is approximately equal around the entire feed through hole 122) is from about 0.25 mm to about 4 mm, from about 1 mm to about 3 mm, from about 0.5 mm to about 3 mm, from about 1 mm to about 2 mm, about 0.25 mm to about 2 mm, or from about 0.5 mm to about 2 mm. The gap 445 could be decreased to zero if the plug 440 is introduced as a liquid to fill the hole and then solidified to its final form to provide mechanical rigidity. Alternatively, where the plug 440 is a solid material, a frit or other material can be used to adhere and/or seal the plug 440 to the back glass sheet 120, 220.

[0056] In some cases multiple feed through holes 122 are required. Fig. 7 A illustrates the case of having two feed through holes 122. These holes can be plugged individually, as shown in Fig. 7B. The use of plug 440 also enables enlarging the feed through hole 122 significantly such that a single larger feed through hole can be used instead of multiple smaller holes, as shown in Fig. 7C. Generally, in such embodiments, the gap 445 distance for the larger non-circular holes may be the same as that for the circular holes. Figs. 7D-7F provide alternative embodiments where the number of feed through holes 122 is increased to four or alternatively, substituted with a single, larger feed through hole.

[0057] Because the plugs 440 by themselves do not provide much support to the back glass plate 120, 220, in some cases they do not significantly help to improve the resistance to fracture of the back glass during hail impact. However, in some embodiments it is possible to seal the feed through holes 122 with a glass frit, for example a low temperature glass frit, to adhere the plug 440 to the substrate and essentially strengthened the glass back sheet 120, 220. Such glass frit seals are known in the art and methods of using them to adhere or seal glass articles are well known and include directed heating methods, such as with lasers.

[0058] Integrating the plugs 440 into the process of making the PV devices may be done via a number of methods. In some embodiments, the plug 440 can be integrated into the lamination process. In some embodiments, the plug 440 could be integrated after the lamination process. Solid plugs 440 such as those made of glass, ceramic, or polymer, could be integrated into the lamination process, using the encapsulant as the adhering agent. The plug 440 would be stacked up along with the other glass, cells, and encapsulant components to go into the lamination cycle. It is at this stack-up point that the electrical leads 116 could be fed into gap 445 between the feed through hole edge 180 and plug edge 1810. In some cases, the plug 440 would have the same thickness as the back glass. Another option is to place the plug 440 into the feed through hole 122 after the lamination process. Solid plugs 440 would be difficult to use at this point since encapsulant 112 leaks into the feed through hole 122 area, creating an irregular surface on which to mount the plug. In some embodiments, a polymer or similar material could fill the hole as a liquid and then "cure" into a solid form.

[0059] Another embodiment described herein includes a stiffening element comprising a stiffening plate 510. In embodiments, stiffening plate 510 is mounted to the back of the module, between the junction box 128 and the back glass 120, 220 or as or as part of the junction box 128 as shown in Figs. 5A and 5B. This stiffening plate 510 locally increases the stiffness of the back glass 120, 220 and/or module and reduces the risk of hail induced fracture from the edge 180 of the feed through hole 122. One embodiment described herein is a stiffening plate 510 that at least partially circumscribes the feed through hole 122. The stiffening plate 510 comprises a generally rigid structure that is dimensionally larger than the feed through hole 122 such that it provides sufficient support or structural integrity to the edge(s) 180 of the feed through hole 122 and/or back glass 120, 220 such that the back glass isn't damaged or destroyed under commercial or industry design qualifications or standards or field tests.

[0060] The stiffening plate 510 geometry may essentially be any geometry that sufficiently protects the feed through hole 122 and provides the necessary structural support. Generally, the stiffening plate 510 is dimensionally larger than the feed through hole 122 and has one or more small holes 550 to allow for the electrical leads 116 to enter the junction box 128. An embodiment of the stiffening plate 510 is shown in Fig. 8 for a single feed through hole 122 configuration. The feed through hole 122 and plug 440 are identified by the dotted lines looking through the stiffening plate 510. Holes 550 are placed in the stiffening plate 510 to allow the electrical leads 116 to pass there through. Holes 550 in stiffening plate 510 can be designed to be as small as possible to maximize the support that the plate gives. Hole 550 may have a diameter from about 1 mm to about 10 mm or more. In some embodiments hole 550 diameter is from about 3 mm to about 8 mm, from about 4 mm to about 7 mm, or from about 6 mm. In embodiments, a single hole 550 or multiple holes 550 can be used to allow feed through of the electrical leads 116. Similarly, Fig. 9 provides an alternative embodiment where two feed through holes 122 are used and a single stiffening plate 510 covers both feed through holes 122 and provides two holes 550 in stiffening plate 510 - one for each feed through hole 122. Referring to Fig. 10, a third embodiment shows a feed through hole 122 with an oval configuration and stiffening plate 510 having two holes 550 (Fig. 10A) or a channel 551 (Fig. 10B) that allows for electrical leads 116 to exit the device.

[0061] The stiffening plate 510 can be located on the outer face of the back sheet 120, 220 (e.g., Fig. 5A) or alternatively, on the inner face (Fig. 16), or both the inner and outer faces to make a sandwich structure. In some embodiments, the stiffening plate 510 is used in combination with a design that shifts the location of the feed through hole 122 to the center of the stack.

[0062] The stiffening plate 510 properties can play a significant role in how effective the stiffening plate 510 is at supporting the back glass substrate. Generally, the CTE of the plate material is less critical than the CTE of the plug 440. In some embodiments, the stiffening plate 510 CTE is from 0 ppm/°C to about 100 ppm/°C from 25°C to 300°C. In some embodiments, the CTE of the stiffening plate 510 is correlated to the CTE of the back sheet. In such embodiments, the plug 440 CTE may be within ±50 ppm/°C, ±30 ppm/°C, ±10 ppm/°C, ±8 ppm/°C, ±5 ppm/°C, or ±2 ppm/°C of the CTE of the back glass. In some embodiments, in order to retain a compressive stress on the back sheet the CTE of the stiffening plate 510 is 10, 20, 30, 40, 50, or 60 ppm/°C greater than the CTE of the back glass. In some embodiments the elastic modulus of the stiffening plate 510 is critical. In those embodiments, the stiffening plate 510 can have an elastic modulus of from about -2 GPa to about 220 Gpa, or alternatively, about 60 GPa to about 220 Gpa.

[0063] The stiffening plate 510 may comprise any material that is compatible with the materials in the photovoltaic module and provides the requisite properties. The stiffening plate 510, in some embodiments, may comprise glass, ceramic, glass ceramic, metal, polymer, or combinations thereof. Because of the fact that electrical leads 116 are passing near the stiffening plate 510, it is generally not made of conductive materials or if it is, such materials are coated, or used in combination with, non-conductive materials. In some embodiments, the stiffening plate 510 comprises a glass material. In some embodiments, the glass of the stiffening plate 510 is compositionally similar to or identical to, the composition of the glass back sheet. This is advantageous in that the stiffening plate 510 and glass back sheet then have equivalent physical properties, such as CTE, hardness, etc. In some embodiments, it is advantageous for the stiffening plate 510 to add a compressive stress to the feed through hole 122. In such embodiments, the stiffening plate 510 may comprise a glass composition with a higher CTE than the CTE of the glass composition comprising the back sheet.

[0064] The stiffening plate 510 itself should be sufficiently strong to provide the structure stiffness necessary to prevent damage to the feed through hole edge 180. In some embodiments, the plate should have flexural stiffness approximately equivalent or greater than a sheet of about 2 to about 4 mm thick soda lime glass. Levels of stiffness in this range would provide adequate support for devices comprising two sheets of 1.0 mm thin specialty glass. As the module glass thickness increases, less stiffness is required of the plate, such that it could be made thinner or of less stiff materials. An example of a material for the stiffening plate 510 would be a tempered soda lime glass sheet of from about 2 mm to about 4 mm thickness.

[0065] Integrating the stiffening plate 510 into the process of making the PV devices may be done via a number of methods. Processing of backing plates fall into two main categories. Those that are integrated into the junction box 128 and those that are separate from the junction box 128. An integrated junction box 128/stiffening plate 510 would be mated to the module at the same point in the process as would a standard junction box. These are adhered using a moisture resistant adhesive such as RTV. Stiffening plates 510 that are separate from the junction box 128 could be mounted during the lamination process using the encapsulant 112 as an adhesive. They could also be mounted to the module after lamination and prior to mounting the junction box 128, using an appropriate adhesive.

[0066] Another aspect comprises a combination of the plug 440 with the stiffening plate 510. While the stiffening plate 510 can be used with (Fig. 5B) or without (Fig. 5A) the thin glass plug 440B, in some embodiments, this stiffening plate 510, by itself, does not provide support for the front glass 110, 210 over the feed through hole 122. Therefore, in some embodiments, it is advantageous to use the two elements (440, 510) in combination. Fig. 5B shows one embodiment comprising a thin glass plug 440B in combination with a stiffening plate 510 adjacent to the junction box 128. Figs. 12 and 13 show alternative embodiments comprising a thin glass-thin glass PV module with a plug 440 and stiffening plate 510 as a single integrated element (Fig. 12) or a thin glass-thick glass PV module with a plug 440 and stiffening plate 510 integrated into one element (Fig. 13). In the case where the plug 440 and stiffening plate 510 are integrated into a single element, that element can have a structure similar to any of those described above regarding the plug 440 and/or stiffening plate 510. For example, the combined element may have a plug region having a beveled (or square) edge 1810 and a plate region that is dimensionally larger than and overlaps the feed through hole 122. Further, even though the plug 440 and stiffening plate 510 are integrated, it is still possible for them to be made of distinct materials that optimize their properties.

[0067] Another aspect comprises integrating either the plug 440 or stiffening plate 510 or both into the junction box 128 itself. Fig. 11 shows one such embodiment wherein the module comprises a thin glass plug 440B along with a stiffening plate 510 integrated into the junction box 128. An alternative embodiment is shown in Fig. 14, where a glass plug 440 is combined with a stiffening plate 510 integrated into the inside of the junction box 128. Such an embodiment would allow direct contact of the junction box 128 with the back sheet 120, 220, potentially improving water resistance. Another embodiment is shown in Fig. 15, where the junction box 128 is edge mounted with a glass plug 440 and integrated stiffening plate 510. In the case where the plug 440 or stiffening plate 510 are integrated into the junction box 128, that element can have a structure similar to any of those described above regarding the plug 440 and/or stiffening plate 510. Further, even though the plug 440 and/or stiffening plate 510 are integrated into the junction box 128, it is still possible for them to be made of distinct materials that optimize their properties.

[0068] As noted above, glasses are particularly well suited for use in PV devices, not only for the front sheet, but also the back sheet, plug 440, and stiffening plate 510. In addition to traditional soda lime glasses, a number of other specialty glasses may be useful in one or more of these aspects. Glass compositions that are useful in embodiments comprise most, if not all, glass compositions, such as soda lime glass. In particular, specialty thin glasses may be particularly useful. In one embodiment, the substrate is made from an alkali-free boroaluminosilicate glass composition, such as those in U.S. Patent Nos. 7,534,734, 7,696,113, 7,935,649, 7,851,394, 8,640,498, and 8,642,491, all of which are incorporated by reference in their entireties. An exemplary alkali boroaluminosilicate glass composition comprises from about 64 mol% to about 71 mol% Si0₂; from about 9 mol% to about 12 mol% A1₂0₃; from 7 mol% to about 12 mol% B₂0₃; from 1 mol% to about 3 mol% MgO; from 6 mol% to about 11.5 mol% CaO; from 0 mol% to about 1 mol% Sn0₂; and is substantially free of alkalis, barium, arsenic, and antimony.

[0069] In another embodiment, the substrate is made from an alkali aluminosilicate glass composition. An exemplary alkali aluminosilicate glass composition comprises from about 60 mol% to about 70 mol% Si0₂; from about 6 mol% to about 14 mol% A1₂0₃; from 0 mol% to about 15 mol% B₂0₃; from 0 mol% to about 15 mol% Li₂0; from 0 mol% to about 20 mol% Na₂0; from 0 mol% to about 10 mol% K₂0; from 0 mol% to about 8 mol% MgO; from 0 mol% to about 10 mol% CaO; from 0 mol% to about 5 mol% Zr0₂; from 0 mol% to about 1 mol% Sn0₂; from 0 mol% to about 1 mol% Ce0₂; less than about 50 ppm As₂0₃; and less than about 50 ppm Sb₂0₃; wherein 12 mol% < Li₂0 + Na₂0 + K₂0 < 20 mol% and 0 mol% < MgO + CaO < 10 mol%. This alkali aluminosilicate glass is described in U.S. Patent No. 8,158,543, herein incorporated by reference.

[0070] Another exemplary alkali-aluminosilicate glass composition comprises at least about 50 mol% Si0₂ and at least about 11 mol% Na₂0. In some embodiments, the glass further comprises A1₂0₃ and at least one of B₂0₃, K₂0, MgO and ZnO, wherein -340 + 27.1·Α1₂0₃ - 28.7·Β₂0₃ + 15.6-Na₂0 - 61.4·Κ₂0 + 8.1-(MgO + ZnO) > 0 mol%. In particular embodiments, the glass comprises: from about 7 mol% to about 26 mol% A1₂0₃; from 0 mol% to about 9 mol% B₂0₃; from about 11 mol% to about 25 mol% Na₂0; from 0 mol% to about 2.5 mol% K₂0; from 0 mol% to about 8.5 mol% MgO; and from 0 mol% to about 1.5 mol% CaO as is described in U.S. Patent No. 9,290,413 by Matthew J. Dejneka et al, entitled "Ion Exchangeable Glass with High Compressive Stress," filed July 1, 2011, the contents of which are incorporated herein by reference in their entirety.

[0071] Other types of glass compositions besides those mentioned above and besides alkali-aluminosilicate glass composition may be used. For example, alkali- aluminoborosilicate glass compositions may be used. Examples of glass compositions may be found in U.S. Patent Nos. 7,666,511, 5,674,790, and 4,483,700, and U.S. Patent Application Nos. 12/277,573, 12/392,577, 12/573,213, 12/856,840, 12/858,490, 13/305,271, 13/305,051, 13/569,756, 13/890,638, and 14/260,625, all of which are incorporated by reference in their entireties.

[0072] The glass sheets used in the devices described herein can be any thickness that is reasonably useful for embodiments described. However, it is often ideal to make the PV modules as light as possible while still retaining structural rigidity. Additionally, use of thinner glass results in less light loss in the material. Any suitable glass thickness can be used. Glass sheet embodiments may have a thickness of about 4 mm or less, about 3 mm or less, about 2.9 mm or less, about 2.8 mm or less, about 2.7 mm or less, about 2.6 mm or less, about 2.5 mm or less, about 2.4 mm or less, about 2.3 mm or less, about 2.2 mm or less, about 2.1 mm or less, about 2.0 mm or less, about 1.9 mm or less, about 1.8 mm or less, about 1.7 mm or less, about 1.6 mm or less, about 1.5 mm or less, about 1.4 mm or less, about 1.3 mm or less, about 1.2 mm or less, about 1.1 mm or less, about 1.0 mm or less, 0.9 mm or less, 0.8 mm or less, 0.7 mm or less, 0.6 mm or less, 0.5 mm or less, or 0.4 mm or less. Some glass sheet embodiments may have thickness of from about 200 μπι to about 3 mm, from about 500 μπι to about 3 mm, from about 200 μπι to about 2 mm, from about 200 μπι to about 1 mm, from about 400 μπι to about 2.5 mm, from about 400 μπι to about 2 mm, from about 400 μπι to about 1 mm, from about 600 μπι to about 1.5 mm, from about 3 mm to about 1 mm, from 2.5 mm to about 1 mm, from 2.0 mm to about 1.0 mm, from 2.0 mm to about 1.5 mm, from about 1.2 mm to about 3.5 mm, from about 1.5 mm to about 3.5 mm, from about 1.5 mm to about 3.0 mm, from about 1.5 mm to about 2.5 mm, or from about 1.5 mm to about 2.0 mm.

[0073] The front sheet 110, 210 and/or back sheet 120, 220 can comprise at least one glass sheet and may optionally further comprise polymer, metal or metallic sheets along with organic, or inorganic coatings, surface modifications, or other modifications to make them suitable for use in photovoltaic applications. Other modifications can include edge preparations, holes or slots for edge sealing, junction boxes 128, brackets or framing, etc.

[0074] Embodiments of the photovoltaic modules described herein may further comprise sealants, encapsulants, fillers, drying agents, ultraviolet radiation absorbers, and other materials. In some embodiments, the PV module may further comprise polymeric materials that may act as sealants, encapsulants, fillers, ultraviolet radiation absorbers, and other materials. In some of these embodiments, the polymers acting to prevent moisture ingress are below their glass transition temperature at all temperatures that the PV module will be exposed to. In some embodiments, the glass transition temperature of the polymeric materials comprising the encapsulant, sealant, or filler can have a glass transition temperature (Tg) of greater than 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, or 95°C. Some of the polymers used in PV modules can degrade forming products that can be potentially harmful to the device, such as, for example, poly(ethylene vinyl acetate) that can degrade in the presence of water into acetic acid. In some embodiments, the polymers used can comprise materials decrease thermal or UV radiation-induced degradation into caustic or other materials that could be harmful to the device. [0075] Embodiments can comprise encapsulants, such as, for example, copolymers, poly(ethylene vinyl acetates) (EVA), poly(vinyl acetals) (e.g., poly(vinyl butyrals) (PVB)), polyurethanes, poly(vinyl chlorides), polyethylenes (e.g., linear low density polyethylenes), polyolefin block copolymer elastomers, copolymers of a-olefins and α,β-ethylenically unsaturated carboxylic acid esters) (e.g., ethylene methyl acrylate copolymers and ethylene butyl acrylate copolymers), silicone elastomers, epoxy resins, and combinations of two or more of these polymeric materials, and ionomers, such as DUPONT'S^® PV5400, PV5300, PV5200, or PV8600. Embodiments also can comprise sealing materials to decrease or prevent moisture ingress, such as a butyl sealant or silicone sealant, at the module perimeter or junction box. Embodiments also can comprise adhesives or glues, such as epoxy or silicone, which may be applied in a liquid, paste, or solid form, such as a roll or tape.

[0076] In some embodiments, a functional layer (not shown in the Figures) can be disposed on the sun side or device side of the front glass plate. The functional layer can be selected from an anti-glare layer, an anti-smudge layer, a self-cleaning layer, an anti- reflection layer, an anti-fingerprint layer, an ultra-violet protection layer, an optically scattering layer, and combinations thereof.

[0077] In some embodiments, one or more additional glass sheets can be incorporated into the PV module, either inside or outside the front or back glass sheet. The additional sheet may be useful as a structural component and may or may not have sodium in its composition. The additional glass sheet can have a thickness sufficient to add structural stability to the device. In some embodiments, the additional glass sheet can have a thickness from about 1.2 mm to about 3.5 mm, from about 1.5 mm to about 3.5 mm, from about 1.5 mm to about 3.0 mm, from about 1.5 mm to about 2.5 mm, or from about 1.5 mm to about 2.0 mm. In some embodiments, the additional glass sheet can have a thickness of about 1.5 mm, about 1.6 mm, about 1.7 mm, about 1.8 mm, about 1.9 mm about, 2.0 mm, about 2.1 mm, about 2.2 mm, about 2.3 mm, about 2.4 mm, about 2.5 mm, about 2.6 mm, about 2.7 mm, about 2.8 mm, about 2.9 mm, about 3.0 mm, about 3.1 mm, about 3.2 mm, about 3.3 mm, about 3.4 mm, or about 3.5 mm. Examples

[0078] Example 1. A number of designs are identified for addressing the increased hail- induced glass fractures at the feed through hole due to the use of thin untempered specialty glasses in PV modules. They are (1) decreasing the size of the feed through hole 122 (2) increase the strength of the feed through hole edge 180 (3) adhering a glass member onto the front of the module and (4) increasing the stiffness of the potting material 130 inside the junction box 128.

[0079] Decrease feed through hole size: Decreasing the size of the feed through hole 122 decreases the stress on the front glass sheets 110, 210 during a hail impact. The diameter of the feed through hole 122 represents the length of unsupported glass in the font glass sheet 110, 201. Thus, decreasing the diameter of the feed through hole 122 increases the support given to the front glass sheets 110, 210 on top of the feed through hole 122. Hail tests are done with various thickness front glass sheets 110, 210 laminated to tempered sheets of soda lime glass 120, 220 with various sized feed through holes 122. These test devices comprise only glass laminates and do not include the cells or junction box. The bar graph in Fig. 3A gives some baseline performances with a 19 mm diameter feed through hole 122 in tempered soda lime glasses 120, 220 of 3.2 mm and 4.0 mm thick. This graph also illustrates the problem with decreasing glass thickness and the corresponding increase in fracture rate. In Fig. 3A, region 300 in each bar shows the number of back glass sheet fractures; region 310 in each bar shows the number of front glass sheet fractures from edge impact; and region 310 in each bar shows the number of front glass sheet fractures from center impact. The graph in Fig. 3B shows that decreasing the feed through hole 122 size dramatically reduces the fracture rate.

[0080] It is found that decreasing the size of the feed through hole 122 is only effective for decreasing the fracture rate of the front glass 110, 210, not the back glass 120, 220. Further, reducing the feed through hole 122 diameter creates issues for processes requiring larger feed through holes. In many processes, a larger feed through hole makes it easier to feed the electrical leads 116 through prior to lamination. Additionally, increasing the size of the feed through hole 122 may provide other opportunities for design improvements and cost savings during module manufacture.

[0081] Increase the feed through hole edge strength: Increasing the strength of the finishing at the feed through hole edge 180 improves the performance of the back glass sheet 120, 220 during hail testing. However, there are two drawbacks to this method. First, additional costs are required to achieve the higher strength. Second, any processes performed on the module after glass manufacturing and junction box mounting exposes the feed through hole 122 to additional damage. Regardless of how high the strength of the feed through hole 122 is, damage after finishing feed through hole 122 can decrease the strength and determine actual performance.

[0082] Adhere a glass member on the front of the module: A transparent glass member can be adhered to the front of the module over the feed through hole 122 to provide additional strength to the front glass sheet 110, 210 in that region. The glass member is larger than the feed through hole 122 and increases the robustness of the module against hail at the feed through hole 122. Potential negative aspects of this are the decreased cosmetic attributes, local decreased transmission, reliability of another adhesive interface, and manufacturing conveyance difficulties.

[0083] Increase stiffness of potting material in junction box: In general, white it is predicted that increasing the stiffness of the encapsulant 12 would provide improved hail performance, testing of several different potting materials shows this method to be ineffective. The negative aspects of modifying potting materials 130 is the limits it puts on manufacturers for device design. Plus, using a potting material 130 has been associated with arcing-induced fires because the potting material 130 holds the connectors in close proximity, allowing them to arc.

Claims

1. A photovoltaic module comprising: a crystalline silicon wafer photoactive region; or an amorphous silicon, CIGS, or CdTe thin film photoactive region; a front glass substrate having a thickness and a coefficient of thermal expansion, a back glass substrate having a thickness and a coefficient of thermal expansion and comprising at least one feed through hole, at least one electrical lead extends from outside the photovoltaic module to the crystalline silicon wafer or thin film photoactive region via the feed through hole; a junction box, and at least one stiffening element, wherein the stiffening element comprises: a plug having a dimension such that at least part of it can fit in the at least one feed through hole; or a stiffening plate having at least one hole and having a dimension such that it a least partially covers the feed through hole; wherein the presence of the at least one stiffening element improves the performance attributes of the photovoltaic module when subjected to IEC-61215 in the case of the crystalline silicon photoactive region or IEC-61646 standards in the case of the thin film photoactive region.

2. The photovoltaic module of claim 1, wherein the plug comprises a glass.

3. The photovoltaic module of claim 1 or claim 2, wherein the plug has a CTE of from about 0 ppm/°C to about 30 ppm/°C from 25°C to 300°C.

4. The photovoltaic module according to any one of the preceding claims, wherein the plug has a CTE within about ±10 ppm/°C of the CTE of the back glass.

5. The photovoltaic module according to any one of the preceding claims, wherein the plug has an elastic modulus of about 10 GPa to about 220 Gpa.

6. The photovoltaic module according to any one of the preceding claims, wherein the plug has a thickness and coefficient of thermal expansion within about ±20% of the back glass sheet.

7. The photovoltaic module according to any one of the preceding claims, wherein the plug has a dimension such that at least one electrical lead can be fed through the gap between the plug feed through hole in the back glass substrate.

8. The photovoltaic module according to any one of the preceding claims, wherein the plug has a dimension of about 0.5 mm smaller than the feed through hole.

9. The photovoltaic module according to any one of the preceding claims, wherein the stiffening plate comprises a glass, a polymer, a metal, or combinations thereof.

10. The photovoltaic module according to any one of the preceding claims, wherein the stiffening plate has a CTE of from about 0 ppm/°C to about 100 ppm/°C from 25°C to 300°C.

11. The photovoltaic module according to any one of the preceding claims, wherein the stiffening plate has a CTE within about ±50 ppm/°C of the CTE of the back glass.

12. The photovoltaic module according to any one of the preceding claims, wherein the stiffening plate has an elastic modulus from about 10 GPa to about 220 Gpa.

13. The photovoltaic module according to any one of the preceding claims, wherein the stiffening plate has a CTE within about ±50% of the back glass sheet.

14. The photovoltaic module according to any one of the preceding claims, wherein the plug and the stiffening plate comprise the same material.

15. The photovoltaic module according to any one of the preceding claims, wherein the plug and the stiffening plate comprise different materials.

16. The photovoltaic module according to any one of the preceding claims, wherein the plug and the stiffening plate comprise a single element physically, chemically, or mechanically bonded together.

17. The photovoltaic module according to any one of the preceding claims, wherein at least one of the plug and the stiffening plate is physically, chemically, or mechanically bonded to the junction box.

18. The photovoltaic module according to any one of the preceding claims, wherein the thickness of at least one of the front glass substrate and the back glass substrate is 2 mm or less.

19. The photovoltaic module according to any one of the preceding claims, wherein the at least one hole in the stiffening plate has a diameter of 3 mm or less.