TWI383509B - A method of stacking solar cells - Google Patents

Description

Method for flip chip stacking solar cells

The invention provides a technical field of a method for crystallizing stacked solar cells, in particular, a solar cell with simple manufacturing and high efficiency.

In recent years, due to the increasing emphasis on environmental protection in many countries around the world, many countries have introduced new energy policies to subsidize the development and application of environmentally friendly energy. Therefore, the market for solar cells has grown rapidly in recent years, with relevant research statistics, at least 16% per year. In 1997, it even grew by 40%. At present, the prospect of solar cells is promising. It is expected that the demand in the future will reach 10 times of the demand in 1997. It can be seen that the global solar power market is growing quite fast.

The ultimate goal of human development of solar cells is to replace the current traditional energy sources. The energy of the sun is inexhaustible. If we can effectively use this resource, we can not only solve the problem of consumable energy. Even environmental issues can be solved together.

The spectrum of sunlight can be divided into three wavelengths: long wavelength (such as far infrared light), short wavelength (such as ultraviolet light) and medium wavelength (such as visible light); while solar cells convert sunlight into solar energy to generate electricity. The purpose.

At present, there are two main factors in the bottleneck of solar cell development:

First, efficiency:

In the photo-electric conversion process, not all incident spectra can be absorbed by the solar cell and completely converted into current. About half of the spectrum energy is too small (less than the energy gap of the semiconductor), and there is no contribution to the output of the battery. offer. While the other half of the spectrum is absorbed by the solar cell, about half of the energy is released before the energy required by the battery-hole pair is released; so the maximum efficiency of a single battery is about 25%. At present, the efficiency of the laboratory can reach the highest level of theoretical value. If you want to improve efficiency, it is necessary to connect a plurality of solar cells of different kinds and materials in the direction of illumination.

Second, the price

There are many kinds of solar cells, and depending on the type of materials, they can be divided into single crystal germanium, polycrystalline germanium, amorphous germanium, III-V group, II-VI group, etc., while solar cell conversion efficiency and material energy gap, light absorption Coefficients, and carrier transfer characteristics, many factors limit the performance of solar cells, such as 矽 series of solar cells, innately belong to the non-direct energy gap material (INDIRECT BANDGAP), when converting light into electricity, it is hot The way to lose most of the energy, so the efficiency is not high. Compound semiconductors, innately belong to the direct energy gap material (DIRECT BANDGAP), convert most of the energy in the way of generating an electronic electric pair when converting light into electricity, so the efficiency is high. However, due to the high cost of compound epitaxy, the complex mass production of the manufacturing process is not easy, so the terminal price is generally high and does not meet economic benefits.

Today's solar cells include tantalum solar cells that incorporate an atom having five valence electrons, such as a phosphorus atom, to form an N-type semiconductor in the crucible; likewise, doping a trivalent atom, such as boron, in the crucible Atom forms a P-type semiconductor; when P-type and N-type semiconductors are in contact with each other, electrons in the N-type semiconductor will flood into the P-type semiconductor to fill the holes therein; near the PN junction, due to electron-electricity The combination of holes forms a load Sub-depletion regions, and thus P-type and N-type semiconductors, respectively, have negative and positive charges, thus forming a built-in electric field.

When sunlight illuminates the PN structure, P-type and N-type semiconductors generate electron-hole pairs due to absorption of sunlight; due to the built-in electric field provided by the depletion zone, electron-holes generated in the depletion zone can be generated. A solar cell is formed by flowing in a semiconductor and then drawing current through an electrode.

However, since the tantalum solar cell can only absorb a part of the wavelength of sunlight, the effect of absorbing the wavelength is only 15-17%.

Therefore, there is a multi-junction compound solar cell, which is formed on a substrate to form a compound semiconductor to absorb the solar spectrum. Due to the direct energy gap relationship, the efficiency is high, but the absorption wavelength effect is only about 25%. Referring to FIG. 4A to FIG. 4C; as shown in FIG. 4A, the solar cell system includes a substrate (60) having a 矽, 锗 or 矽/锗, and the substrate (60) is grown. A PN junction semiconductor layer (61) capable of absorbing long wavelengths (such as infrared light), such as germanium (Si) / germanium (SiGe).

As shown in FIG. 4B, the solar cell system includes a substrate (70) having gallium arsenide or arsenic or gallium phosphide, and the substrate (70) is grown with a PN junction semiconductor layer capable of absorbing intermediate wavelengths (such as visible light) ( 71), such as gallium arsenide (GaAs) / aluminum gallium arsenide (AlGaAs).

As shown in FIG. 4C, the solar cell system includes a substrate (80) having Al ₂ O ₃ sapphire, tantalum carbide or ZnO, and the substrate (80) is grown with a PN junction semiconductor capable of absorbing short wavelengths (such as ultraviolet light). Layer (8 1), such as gallium nitride (GaN) / aluminum gallium nitride (AlGaN).

However, due to the above-mentioned compound solar cell, it is only possible to separately absorb long-wavelength light energy (as shown in FIG. 4A), absorb medium-wavelength light energy (as shown in FIG. 4B), or absorb short-wavelength light. Can (as shown in Figure C).

Therefore, there is a multi-joined tandem cell which is epitaxially grown in a battery with different energy gaps; as shown in FIG. 5A, the solar cell includes a crucible, a crucible or The 矽/锗 substrate (60) is stacked on the substrate (60) with a PN junction semiconductor layer (61) capable of absorbing long wavelengths, such as 矽(Si)/矽锗(SiGe), which can absorb long wavelength light, and then A conductive via layer (10) is grown thereon, and the conductive via layer (10) is further stacked with a PN junction semiconductor layer (71) capable of absorbing a medium wavelength, such as gallium arsenide (GaAs), and then grown to be electrically conductive. A pass-through layer (10) is further disposed on the conductive via layer (10) with a PN-bonded semiconductor layer (72) capable of absorbing a medium wavelength, such as aluminum gallium arsenide (AlGaAs) or indium gallium phosphide (InGaP).

Similarly, as shown in FIG. 5B, the solar cell system includes a substrate (70) of gallium arsenide or arsenic or gallium phosphide, and a PN junction semiconductor layer (71) capable of absorbing a medium wavelength is stacked on the substrate (70). For example, gallium arsenide (GaAs) is further grown on a conductive via layer (10), and the conductive via layer (10) is further stacked with a PN junction semiconductor layer (72) capable of absorbing a medium wavelength, such as aluminum arsenide. Gallium (AlGaAs), indium gallium phosphide (InGaP).

However, due to the above semiconductors, bismuth (Si) / germanium (SiGe), gallium nitride (GaN) / aluminum gallium nitride (AlGaN), gallium arsenide (GaAs) / aluminum gallium arsenide (AlGaAs) and other materials are large. Not the same, so semiconductor epitaxial stacking When growing up, it is easy to produce cross-contamination, and the lattice matching is also different; causing problems such as a decline in production yield and low efficiency.

Accordingly, the present inventors have solved the problems of the above-mentioned conventional solar cells, and after years of research and manufacturing development in related fields, after detailed design and careful evaluation, finally created a kind of improvement of the above disadvantages, and more A method for flip chip stacked solar cells with ideal utility.

Conventional multi-junction solar cells, need to put Different material layers directly epitaxially grow to capture all energy photons, but the crystal lattice difference is too large, and the tension will damage the crystal. Therefore, the most multi-functional multi-junction battery is only two or three layers, and Low reliability.

The invention provides a flip chip stack too The method of the cation battery includes the steps of: (1), growing a plurality of flat-plate type PN junction semiconductor layers, and allowing each PN junction semiconductor layer to respectively absorb materials of various wavelengths of light; and step 2 (S2), each plate When the PN junction semiconductor layer is a different series of materials, a tunneling conductive layer can be grown between the PN junction semiconductor layers to increase the conductivity between the PN junction semiconductor layers; Step 3 (S3), using the flip chip technology stacking step 1 Each of the PNs of (S1) is bonded to the semiconductor layer, and each of the PN junction semiconductor layers may be sequentially stacked from a long wavelength to a short wavelength.

Thereby, the present invention uses the flip chip technology to stack solar cells, which can be increased. The electrical efficiency of the solar cell makes the battery easy to match, and the disadvantages of the conventional battery being difficult to match are improved.

Providing a flip chip stacked solar cell The method of flip chip bonding is convenient for bump bonding, thereby achieving solar cells with simple manufacturing and low cost, and improving the difficulty of matching conventional batteries, and since the flip chip technology utilizes bump bonding, in thermal cycling. There is a higher yield in the test.

The above-mentioned objects, structures and features of the present invention will be described in detail with reference to the preferred embodiments of the present invention. .

First, referring to the first figure, a method for flip-chip stacked solar cells according to the present invention mainly uses flip chip technology to stack solar cells on a flip chip substrate, and the steps thereof include: step one (S1), growth The plurality of flat-plate type PN-bonded semiconductor layers, and each of the PN-bonded semiconductor layers can respectively be made of materials of various wavelengths of light; in step 2 (S2), when each of the flat-plate type PN-bonded semiconductor layers is a different series of materials, the PN-bonded semiconductor layers can be interposed between the layers. Growing a tunneling conductive layer to increase the conductivity between the PN junction semiconductor layers; in step 3 (S3), stacking the PN junction semiconductor layers of step one (S1) by flip chip technology, and making each PN junction semiconductor layer long Wavelength to short wavelength are sequentially stacked.

With the above design, the present invention provides a second A diagram to a second D diagram, which are diagrams of various embodiments of the present invention; As shown in FIG. 2A, the method includes: growing a flat type of absorbing long-wavelength light (such as infrared light), 锗PN bonding semiconductor layer (61), and a substrate of 矽, 锗 or 矽/锗 (60) a flat plate type arsenic, gallium, phosphorus PN junction semiconductor layer (71), (72) and a gallium arsenide or arsenide or gallium phosphide substrate (70) capable of absorbing medium-wavelength light (such as visible light); The flip chip technology stacks an arsenic, gallium, phosphorus PN junction semiconductor layer (71) capable of absorbing medium-wavelength light (such as visible light) on a 锗 PN junction semiconductor layer (61) capable of absorbing long-wavelength light (such as infrared light), (72), wherein the arsenic, gallium, and phosphorus PN junction semiconductor layers (71) and (72) capable of absorbing medium-wavelength light (such as visible light) are on a substrate (70) of gallium arsenide or arsenic or gallium phosphide; Because it can absorb long-wavelength light (such as infrared light), 锗 PN junction semiconductor layer (61), and arsenic, gallium, phosphorus PN junction semiconductor layer (71), (72) that can absorb medium-wavelength light (such as visible light) For different series of materials, a bump (20) can be grown between the two flat-type PN junction semiconductor layers, and two different series can be used in the form of flip chip. The P-N bonding semiconductor layer of the material is bonded.

In addition, as shown in FIG. 2B, the method includes: growing a flat type absorbing 长 long-wavelength light (such as infrared light), 锗PN bonding semiconductor layer (61), and a substrate of 矽, 锗 or 矽/锗(60); growing a flat type nitrogen-containing PN junction semiconductor layer (80) capable of absorbing short-wavelength light (such as ultraviolet light) and a transparent substrate (81) of Al ₂ O ₃ sapphire, tantalum carbide or ZnO; using flip chip The technique stacks a nitrogen-containing PN junction semiconductor layer (80) capable of absorbing short-wavelength light (such as ultraviolet light) on a 锗 PN junction semiconductor layer (61) capable of absorbing long-wavelength light (such as infrared light), wherein the Al ₂ The transparent substrate (81) of O ₃ sapphire, tantalum carbide or ZnO is located on the nitrogen-containing PN junction semiconductor layer (80) capable of absorbing short-wavelength light (such as ultraviolet light); since it can absorb long-wavelength light (such as infrared light) The 矽, 锗 PN junction semiconductor layer (61), and the nitrogen-containing PN junction semiconductor layer (80) capable of absorbing short-wavelength light (such as ultraviolet light) are different series materials, so that a bump can be grown between the two PN junction semiconductor layers ( 20), using a flip chip form to connect PN junction semiconductors of two different series of materials In this embodiment, it is not necessary to grow the tunneling conductive layer between the two PN junction semiconductor layers.

In addition, as shown in FIG. 2C, the method includes: growing a flat type of arsenic, gallium, phosphorus PN junction semiconductor layer (71), (72) and gallium arsenide or the like to absorb medium wavelength light (such as visible light) a substrate of arsenic or gallium phosphide (70); a flat-type nitrogen-containing PN junction semiconductor layer (80) capable of absorbing short-wavelength light (such as ultraviolet light) and a transparent substrate of Al ₂ O ₃ sapphire, tantalum carbide or ZnO (81); using a flip chip technique to stack PN junctions capable of absorbing short-wavelength light (such as ultraviolet light) on arsenic, gallium, and phosphorus PN junction semiconductor layers (71), (72) capable of absorbing medium-wavelength light (such as visible light). a semiconductor layer (80), wherein the transparent substrate (81) of Al ₂ O ₃ sapphire, tantalum carbide or ZnO is located on the nitrogen-containing PN junction semiconductor layer (80) capable of absorbing short-wavelength light (such as ultraviolet light); Arsenic, gallium, phosphorus PN junction semiconductor layers (71), (72) capable of absorbing medium-wavelength light (such as visible light), and nitrogen-containing PN junction semiconductor layers (80) capable of absorbing short-wavelength light (such as ultraviolet light) are different A series of materials, so that a bump (20) can be grown between the two PN junction semiconductor layers, and two different systems can be used in the form of flip chip. PN junction semiconductor material layer is bonded.

Further, as shown in FIG. 2D, the method includes: a germanium, germanium or germanium/tellurium substrate (60) having a flat type PN junction semiconductor layer (61) capable of absorbing long wavelengths, such as germanium. (Si)/矽锗(SiGe), which absorbs long-wavelength light, and then grows a conductive via layer (10), and the conductive via layer (10) is further stacked with an absorbing medium wavelength PN junction. A semiconductor layer (71), such as gallium arsenide (GaAs), is further grown on a conductive via layer (10), and the conductive via layer (10) is further stacked with a PN junction semiconductor layer capable of absorbing intermediate wavelengths (72). For example, aluminum gallium arsenide (AlGaAs) or indium gallium phosphide (InGaP).

In addition, a flat-type nitrogen-containing PN junction semiconductor layer (80) capable of absorbing short-wavelength light (such as ultraviolet light) and a transparent substrate (81) of Al ₂ O ₃ sapphire, tantalum carbide or ZnO are grown; A nitrogen-containing PN junction semiconductor layer (80) capable of absorbing short-wavelength light (e.g., ultraviolet light), stacked on a PN junction semiconductor layer (72) capable of absorbing medium wavelengths; capable of absorbing short-wavelength light (e.g., ultraviolet light) The nitrogen PN junction semiconductor layer (80) and the absorbing junction medium PN junction semiconductor layer (72) are of different series materials, so that a bump (20) can be grown between the two PN junction semiconductor layers, and the two layers can be used in the form of flip chip. A PN junction semiconductor layer of different series of materials is bonded.

In addition, the present invention further provides a preferred embodiment (as shown in the third figure), which comprises: growing a flat type of absorbing long wavelength light (such as infrared light), and 锗PN bonding semiconductor layer (61) For example, bismuth (si)/germanium (SiGe); growing a flat-plate arsenic, gallium, phosphorus PN junction semiconductor layer (71), (72) capable of absorbing medium-wavelength light (such as visible light), such as gallium arsenide (GaAs) / aluminum gallium arsenide (AlGaAs); and, a flat type PN junction semiconductor layer (80) capable of absorbing short-wavelength light (such as ultraviolet light), such as gallium nitride (GaN) / aluminum gallium nitride (AlGaN); A PN junction semiconductor layer (71) capable of absorbing a long-wavelength light (such as infrared light), a 锗PN junction semiconductor layer (61), and a medium-wavelength light (such as visible light) by a flip chip technique (71), 72) and, a PN junction semiconductor layer (80) capable of absorbing short-wavelength light (such as ultraviolet light); 可 接合 junction semiconductor layer (61), absorbable medium wavelength due to absorption of long-wavelength light (such as infrared light) Light, such as visible light, arsenic, gallium, phosphorus PN junction semiconductor layers (71), (72) and nitrogen-absorbing short-wavelength light (such as ultraviolet light) P-N bonded semiconductor layer (80) For different series of materials, a bump (20) can be grown between the two P-N bonded semiconductor layers, and the P-N bonded semiconductor layers of two different series of materials can be bonded by flip chip.

As shown in the above second A to second D and third figures, since the flip chip technique uses the bumps (20) to bond the wafers, the conventional solar cells are connected in series on the plane by means of bonding wires. It is convenient to bond the wafer in the vertical direction and is easy to conduct. Therefore, it can absorb materials of long wavelength (such as infrared), medium wavelength (such as visible light), and materials that can absorb short wavelength (such as ultraviolet light), electrical properties. Preferably (better efficiency), battery pairing is easier, and the invention is simple to manufacture and less costly.

In addition, the present invention can install a lens (not shown in the figure) on the solar cell, so that the lens can concentrate the light beam, so that the sunlight can be absorbed more easily, and the substrate area under the lens can be reduced, so that the invention can be Solar cells can reduce costs.

In summary, the present invention has the above-mentioned numerous performances and practical values, and can effectively improve the overall economic benefit, so the present invention is indeed an innovative invention, and the same or similar products are not seen in the same technical field. The public use shall have met the requirements of the invention patent, and the application shall be made according to law, and the invention patent shall be given.

(S1)‧‧‧Step one

(S2)‧‧‧Step 2

(S3) ‧ ‧ Step 3

(10) ‧ ‧ tunneling conductive layer

(20)‧‧‧Bumps

(60) ‧ ‧ 矽, 锗 or 矽 / 锗 substrate

(61) ‧‧‧Plate type can absorb long-wavelength light (such as infrared light), 锗P-N bonded semiconductor layer

(70) ‧‧‧ Substrate of gallium arsenide or arsenic or gallium phosphide

(71), (72) ‧‧‧ flat-type arsenic, gallium, phosphorus P-N bonded semiconductor layers capable of absorbing medium-wavelength light (such as visible light)

(80) ‧‧‧Plate-type nitrogen-containing P-N bonded semiconductor layer capable of absorbing short-wavelength light (such as ultraviolet light)

(81) ‧‧‧Al ₂ O ₃ sapphire, tantalum carbide or ZnO transparent substrate

The first figure is a flow chart of the method of the invention.

2A through 2D are schematic views of embodiments of the present invention.

The third figure is a schematic diagram of a preferred embodiment of the present creation.

4A to 4C are schematic views of an embodiment of the conventional use.

5A to 5B are schematic views of another embodiment of the conventional use.

(S1)‧‧‧Step one

(S2)‧‧‧Step 2

(S3) ‧ ‧ Step 3

Claims (1)

A method for flip-chip stacking a solar cell, comprising: growing a flat-plate type PN junction semiconductor layer capable of absorbing light having a long wavelength of light or arsenic and phosphorus; growing a light having a shorter wavelength and containing arsenic and phosphorus or containing a flat-plate type PN-bonded semiconductor layer of nitrogen; when growing a germanium-containing or arsenic-phosphorus-containing PN-bonded semiconductor layer, a tunneling conductive layer can be grown to increase conductivity; and finally, it can absorb light having a longer wavelength.矽锗 or a PN-bonded semiconductor layer containing arsenic-phosphorus, at least one arsenic-phosphorus or nitrogen-containing flat-type PN junction semiconductor layer capable of absorbing a shorter wavelength of light, and no need to grow tunneling between the two PN junction semiconductor layers Floor.