CN101246917A

CN101246917A - Method for intensifying light absorption of thin-film solar cell

Info

Publication number: CN101246917A
Application number: CNA2007100049696A
Authority: CN
Inventors: 李沅民; 马昕
Original assignee: BEIJING XINGZHE MULTIMEDIA TECHNOLOGY Co Ltd
Current assignee: BEIJING XINGZHE MULTIMEDIA TECHNOLOGY Co Ltd
Priority date: 2007-02-14
Filing date: 2007-02-14
Publication date: 2008-08-20

Abstract

The present invention discloses a method for increasing light absorption of film solar cell. Firstly, depositing glass beards with diameter less than 1 mum on glass substrate to make the surface has fluctuation structure with propriety mum dimension. Then depositing transparent front electrode to make it has surface structure with evident light scattering effect. The film photovoltaic device formed on the transparent front electrode has higher light absorption capacity and conversion efficiency.

Description

Increase the method for thin-film solar cells light absorption

Technical field

The invention belongs to photovoltaic equipment field, specially refer to the manufacturing technology of the photovoltaic device of based thin film silicon.

Background technology

Recent years, the development of photovoltaic cell and large tracts of land photovoltaic module has caused common people's extensive concern.Especially amorphous silicon hydride and nanocrystal silicon, they demonstrate great potential along with the extensive use of photovoltaic device in commercial and dwelling house facility.Producing distinguishing feature of thin film silicon photovoltaic device under temperature so lower below 260 ℃ is, the semiconductor film relevant of large tracts of land deposition with silicon with electrically contact rete and have premium properties.Simultaneously, use good ripe filming equipment and program, can make to industrialization template cheaply.The laser scribing moulding process (laserpatterning) that is applied to the different films on the same glass substrate allows a plurality of solar cell devices directly to form the large tracts of land photovoltaic module of integrated form in film deposition process, has reduced procedure of processing and has also improved reliability of products.

For photovoltaic device, film photovoltaic device particularly, the key that makes its function admirable is to optimize the absorption of photoelectric conversion semiconductor layer to luminous energy, and reduces the optical loss in the device simultaneously.Can absorb luminous energy to greatest extent in very thin absorbed layer, be the essential condition of high conversion efficiency.The solar cell that the hydrogenation thin film silicon is constituted has the p-i-n structure usually, and wherein p layer and n layer are sluggish " dead layers ", and they set up a built-in electric field in the i of non-doping layer, thereby make photic charge carrier by effective collection.The thickness of its absorbed layer generally has only a hundreds of micron, is no more than about 2000 microns at most.And the absorption coefficient of the ruddiness of hydrogenated silicon film by utilizing and infrared light is all lower, so there is very most sunlight not to be effectively used.P-i-n structure based on hydrogenated silicon film by utilizing is sandwiched in former and later two electrodes (electric contacting layer), and forms complete photovoltaic element.Electrode must have good transparency and conductivity before normally used, and it normally is made of transparent conductive oxide (TCO), such as thickness is the tin oxide that is doped or the zinc-oxide film of 600-900 nanometer.Rear electrode is made of jointly a TCO and metallic film usually, and an one important function is exactly with among the unabsorbed smooth reflected back p-i-n structure.Attempted various ways and improved absorption light, comprising use coarse transparent before electrode.In addition, also use the very high back electrode of reflecting rate, and made unabsorbed light be got back in the battery by throwing again.Can not do very thickly for amorphous silicon battery absorbed layer i layer, reason is the defective that this material has the light quality decay.So remarkable optical design has played decisive role for the conversion efficiency of the thin-film solar cells as the silane.

Usually electrode TCO before employed, such as tin oxide are difficult to be done to such an extent that have surface texture structure or roughness highly when its thickness is no more than 1000 nanometers, that is to say that it is often unsatisfactory to the scattering of light ability.TCO with rough surface often has relatively poor electric conductivity and higher optical loss, this drawbacks limit the film photovoltaic device photoelectric efficiency further improve.Various trials were once arranged, make the surface texture (texture) of TCO become more obvious, for example the TCO film that deposits is carried out chemistry or mechanical treatment, make its surface become more coarse, but the resulting roughening of this way does not have better controlled and repeatability, thereby often causes the defective of film photovoltaic device.Another way is exactly that TCO thickness is increased, and makes its rough surface increase with thickness, but the TCO that thickens causes it that absorption of incident light is increased, and has also prolonged the fabrication cycle of photovoltaic device simultaneously.So, be necessary to seek a kind of moderate TCO of thickness that makes and have the method for higher, controlled surface texture.And this surface texture that is beneficial to light scattering is preferably provided by substrate itself, and does not rely on the forming process of TCO film.

Summary of the invention

Based on above-mentioned consideration, the applicant has worked out primary and foremost purpose of the present invention: improve the conversion efficiency based on the film solar photovoltaic device of silane.

Further purpose of the present invention is, improves the manufacture craft of thin-film solar cells, thereby strengthens the optical characteristics of this device, particularly to the response of longwave optical.

In order to achieve the above object, the present invention adopts a kind of method that increases the thin-film solar cells light absorption.At first sedimentation diameter is lower than 1 micron glass beads on glass substrate, make its surface have the relief fabric of suitable micron-scale, electrode TCO before the deposit transparent makes its acquisition have the surface texture or the graininess (roughening) of obvious light scattering effect then.On this TCO, form p-i-n type photovoltaic cells and reflective back electrode then based on hydrogenated silicon film by utilizing.Semiconductor that these deposit subsequently and back electrode film have kept the rough surface structure of TCO largely.So the sunlight of incident on two interfaces of glass and TCO and TCO and hydrogenated silicon film by utilizing, was subjected to scattering before entering the p-i-n photovoltaic cells.And the longwave optical that is not absorbed by photovoltaic element also is subjected to the reflection of double scattering on two interfaces of back electrode, gets back to photoelectric conversion regions with bigger angle.So the film photovoltaic device according to manufacturing of the present invention has the good optical design, it is very effective for catching weak absorbing light and improving photoelectric conversion efficiency.

Glass substrate plate transparent before before the electrode, just make it have the surface of fluctuating, make the transparency conducting layer that plates below can have higher fluctuating easilier like this, its refracting power to light is strengthened greatly.Obtain higher anaclasis power in this way, more feasible than the way of plating oxide-film at high temperature, and also it also reduces greatly to the thickness requirement of metal oxide film.The feasibility of verified this notion of our experiment.

The present invention is equally applicable to unijunction photovoltaic device that is made of single p-i-n photovoltaic cells and the many knots photovoltaic device that is formed by stacking by a plurality of p-i-n photovoltaic cells.

Description of drawings

The present invention will be further described below in conjunction with drawings and Examples.

Fig. 1 has shown makes transparent preceding electrode have the process of rough surface.

Fig. 2 has shown the layer structure of the thin-film solar cells of making according to the present invention.

Embodiment

As shown in Figure 1, the first step of the present invention is that open and flat glass plate 1 is cleaned up, and uses molten gel sedimentation (sol-gel) glass marble to be plated to the top layer of glass substrate then.Specific practice is that glass plate is immersed the molten gel that contains glass beads and adhesion agent, and constantly stir molten gel or continuous moving substrate itself, thereby make glass beads adhere to the glass substrate appearance uniformly, then glass substrate is taken out from molten gel, be not higher than under 500 ℃ the temperature, heat-treat adhesion agent solidified, make glass beads firm attached on the glass substrate, form a rete 11 with relief fabric.Electrode 2 (TCO) before the deposit transparent on top layer 11 after this, such as tin oxide or zinc oxide have its surface 27 and are similar to surface layer of glass 11 or the higher rough surface of degree.The mean fluctuation degree of its surface texture should be between the 30-80 nanometer, preferably near 50 nanometers.

Formed after this film photovoltaic device structure as shown in Figure 2, this structure comprises: a glass substrate 1, it has the top layer 11 of non-specular surface; A transparent preceding electrode 2; One or more p-i-n type photovoltaic cells 8 that constitute by film based on silane; Second transparent conductive oxide 7 and one or more metallic film 45.Because preceding electrode 2 has the surface of good structure, Sheng Chang hydrogenated silicon film by utilizing 8 and subsequent transparent conductive oxide 7 have kept this surface texture substantially thereafter.That is to say, incident light before entering the p-i-n photovoltaic cells, glass substrate and transparent before the interface 17 of electrode and the interface 27, twice of preceding electrode and thin film silicon be subjected to bigger scattering, make light enter semiconductor optoelectronic transition region 8 with bigger angle.The longwave optical that is absorbed by the p-i-n photovoltaic cells is not subjected to the scattering sexual reflex of wide-angle for twice yet at the interface 77 of the interface 87 of the thin film silicon and second transparent conductive oxide and second transparent conductive oxide and metal film.Thereby make most weak absorbing light enter the p-i-n photovoltaic cells once more with the direction of the critical angle that surpasses whole internal reflections.Thereby their absorbed probability have been improved greatly.So light scattering described in the invention increases effect, and is more obvious along with the increase of base plate glass rough surface, because it has improved the light scattering effect at all rete interfaces, back.

Claims

1. p-i-n type photovoltaic device, its structure comprises successively: a glass substrate; A transparent preceding electrode; One or more p-i-n type photovoltaic cells that constitute by film based on silane; Back electrode with light reflective properties, it can comprise a transparent conductive oxide and one or more metallic film.It is characterized in that: be coated with the glass beads of one deck diameter between the 0.5-1 micron on the glass substrate, make one surface have relief fabric, electrode before the deposit transparent on the glass beads top layer then, comprise tin oxide and zinc oxide, electrode also has similar or more tangible relief fabric before making this transparent, thereby increase sunlight in photovoltaic device scattering and to weak light absorbing capture ability, improve photoelectric conversion efficiency simultaneously.

2. p-i-n type photovoltaic device according to claim 1 is characterized in that: described transparent preceding electrode is the zinc oxide that is no more than 800 nanometers with the thickness that magnetically controlled sputter method forms.

3. p-i-n type photovoltaic device according to claim 1 is characterized in that: described back electrode with light reflective properties is made of a transparent conductive oxide and a non-conductive ultrawhite reverberation.