CN101246951A

CN101246951A - Transparent conductive polymer as amorphous silicon battery p layer

Info

Publication number: CN101246951A
Application number: CN 200710004982
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 application of p type polymer film in amorphous silicon photovoltaic device. The 10-30 nanometer transparent p type polymer produced by vacuum coating can be used as p layer of p-i-n type amorphous silicon solar cell to reduce light absorption loss and improve output power.

Description

Transparent conductive polymer as amorphous silicon battery p layer

Technical field

The invention belongs to the solar energy materials scope, specially refer to the material technology that is applied to film photovoltaic device.

Background technology

In recent years, the exploitation of thin film solar photovoltaic cell and large-area module or template (photoelectric subassembly) has been subjected to worldwide attracting attention.The great potential that amorphous silicon hydride, particularly nanocrystal silicon (nano-silicon) are widely used in commerce and dwelling house photoelectric device shows.A key character is arranged being lower than the hydrogenated silicon film by utilizing photoelectric device of making under 260 ℃ the temperature, when depositing described semiconductor silicon film and electric contacting layer by large tracts of land exactly, use cheap film substrate material and consummate processing method and equipment, make it have the advantage of low production cost and premium properties simultaneously.The laser scoring processing procedure that carries out on same substrate allows a plurality of solar cells formation and by single ground circuit integrated series, directly generates large tracts of land photovoltaic template in the process of thin film deposition.

Photovoltaic (PV) device is called solar cell or photoelectric conversion device again, is used to convert radiant energy (for example sunlight, incandescence or fluorescent) to electric energy.The realization of this conversion is called as photovoltaic effect.When radiation was passed photoelectric device and absorbed by the active region of device, electronics and hole were to having produced.Being come by the electric field separates in the device in electronics and hole, and is collected by external circuit.In the photovoltaic cell with p-i-n type structure, when light radiation was absorbed by intrinsic layer or i layer (absorbed layer), photic electron hole pair formed.Under the influence of built-in electric field, electron stream is to n type conductive region, and the hole flows to p type conductive region, and they are separated, and this flowing based on the electron hole behind the extinction produced the photovoltage and the photoelectric current of photovoltaic cell.

According to the structure of known solar cell based on amorphous silicon or nano-silicon and alloy thereof, built-in electric field forms in by the structure of forming based on p type, i type (intrinsic) and the n type rete of amorphous silicon (a-Si) or nano-silicon (nc-Si) material.A typical p-i-n type solar cell is by forming with the lower part: one has the high grade of transparency and the constitutionally stable first floor or substrate, electrode before the transparent conductive oxide that on substrate, forms (preceding contact layer), a p layer, an i layer, a n layer, another nesa coating, a metal film, the adhesive of a sealing and a protective plate.In operation, sunlight enters the p-i-n structure from the outside of solar cell substrate, though sometimes p type nanocrystal silicon (nc-Si) also is used, but usually selecting material as p layer 6 is a kind of amorphous silicon alloy of boron doped, broad-band gap, for example non-crystal silicon carbon (a-SiC), amorphous silicon nitrogen (a-SiN) or amorphous silica (a-SiO).Photovoltaic " absorbed layer " or i layer (claiming conversion layer again) are made of amorphous silicon, nano-silicon or amorphous germanium silicon alloy usually.The n layer of phosphorus doping is made up of amorphous silicon or nano-silicon usually.Tin-oxide (the SnO that preceding transparent conductive oxide electrode layer is normally mixed by fluorine ₂: F) form.Nesa coating is the zinc oxide (ZnO:Al) of aluminium doping normally.Metal film is aluminium or silver normally.

The very important point is that the semi-conducting material that is used for making photovoltaic device can absorb radiation as much as possible, with the generation electronics and the hole of high yield, and is converted to useful electric energy, improves conversion efficiency.

In the p-i-n type thin film silicon photovoltaic cell of present known technology, the i layer that is clipped in the non-doping between p layer and the n layer is thicker than p layer and n layer far away.The effect of intrinsic i layer is to stop the electron hole compound before being separated by built-in electric field.

The incident light that has is doped layer (p layer and n layer) and absorbs, and is because the carrier lifetime of these layers generation is extremely short, just compound rapidly before being collected.Therefore, in the absorption of doped layer the generation of photovoltaic cell photoelectric current there is not help.Therefore the minimal absorption of doped layer can strengthen the short circuit current of p-i-n type photovoltaic cell.Have one of function of wide bandgap p layer, be exactly the optical absorption loss that reduces the p layer to greatest extent, and do not weaken its contribution built-in electric field.By adjusting the band gap (optical band gap) of p layer, the absorption loss of p layer can be widened material (generally including elements such as carbon, nitrogen, oxygen, sulphur) and minimize by comprising p layer band gap.For example, the p layer is made up of the non-crystal silicon carbon (a-SiC) of the above-mentioned boron doped p of having type conductivity usually.But,, must cause its resistivity to rise to the increase that p layer band gap widened material.Therefore, band gap is widened the concentration (atomic component percentage) of material in the p layer can not be too high, and it is limited by the maximum allowable value of the internal resistance of photoelectric device.Another problem is that the band gap of traditional p layer is still wide inadequately with respect to amorphous silicon i layer, has limited the raising of photovoltage.Be more in addition, the parameter space of the non-crystal silicon carbon alloy p layer that growth is best is very narrow, brings difficulty for the commercial process of photovoltaic panel.The amorphous silicon alloy p layer of optimal broad-band gap has the most highly doped efficient and conductivity, and for example has the optical band gap greater than 2.1-2.2eV.No matter is the performance of the p layer that in single junction cell or the good multijunction cell photovoltage and photoelectric current had the greatest impact based on the photovoltaic technology latest developments of amorphous silicon in part because of having improved.In order to reduce light loss as far as possible, strengthen photoelectric current, the luminous energy band gap of the p layer of a function admirable must be wide as far as possible, and thickness is low as far as possible, and Fermi level is near the edge of valence band, and fully conduction (is higher than 10 such as conductance ^-7Scm ^-1).It also must have compatible characteristic with electrode layer before the transparent conductive oxide and the i layer (or resilient coating) that is close to aspect contact performance and deposition (growth) condition.Extremely thin p layer (about 100

10 nanometers) must have the performance of thick film.Photovoltage mainly is to produce near the p-i interface.Unless use additional boundary layer, the p layer can be set up with nesa coating and contact.In order to improve the efficient of photovoltaic device, low contact " barrier " or effective " tunnel " function are necessary.

It's a pity, amorphous silicon alloy p layer for broad-band gap, owing to the contact barrier of interface with the preceding electrode (preceding contact layer) of transparent conductive oxide, wideer band gap and lower optical loss have caused resistivity to rise and p layer internal resistance rises, thereby have reduced the collection efficiency of photoelectric current.These are fundamental limitations of traditional silicon film solar batteries performance.

For these reasons, seeking one can replace based on the material of the p layer of amorphous silicon alloy highly significant.

Summary of the invention

Based on above-mentioned consideration, the applicant has worked out primary and foremost purpose of the present invention: a material that substitutes traditional broad-band gap amorphous silicon alloy p layer is provided.

It is of the present invention that to advance a purpose be to improve based on hydrogenation non crystal silicon film p-i-n type Solar cell performance.

In order to reach above-mentioned target, the invention provides the semiconductive of had broad-band gap of a novelty or conducting polymer and replace the P layer material that non-crystal silicon carbon alloy for example constitutes, thereby reduce the light absorption that the p layer is caused, therefore improve the efficient of p-i-n type non-crystal silicon solar cell.

Conduction (semiconductive) polymer is a very interesting material, its various character are in recent years by extensive studies, wherein some conducting polymer also is called conductive plastics, some material can make very clear films, to such an extent as to almost can ignore than amorphous silicon alloy the absorption of visible light.Can increase the intensity of photoelectric current greatly if this material can use in the window layers material (p layer) at hull cell, thereby obtain higher photoelectric conversion efficiency.The conducting polymer of broad-band gap can also form heterojunction with non-doped amorphous silicon i layer, produces good photovoltage.

The manufacturing cost of the polymer of not only transparent but also conduction can be very low.Along with the understanding to this class material constantly increases, their manufacturing process is also constantly perfect.The method of the acquisition film conducting polymer (conductive plastics) of comparative maturity comprises: be wider than the nitrogen sulphur long-chain polymer of 2.5 electronvolt with the band gap that the plasma enhanced chemical vapor deposition method is made, and use the polymer of the hydrocarbon formation of arc plasma (negative electrode arc light) formation.The polymer of the insulation that has been formed also can make it have certain conductivity by processed method, for example use the silicon-nitrogen polymer and the acetylene polymer of iodinate.Up-to-date technology can make this material accomplish on the large-area substrate by the way of printing, and this is a kind of very feasible way for producing the large area film solar cell.

Description of drawings

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

Accompanying drawing has shown the layer structure of a p-i-n type thin-film solar cells.

Embodiment

The formation method of a representational conducting polymer is, use the method for vacuum coating, be no more than under 300 ℃ of conditions in temperature, produce the polymer with p type conductivity of thickness in the 10-30 nanometer range, comprise the polymer that nitrogen sulphur long-chain polymer and hydrocarbon constitute.

Above-mentioned p type conducting polymer can be used as the p layer of p-i-n type non-crystal silicon solar cell, reduces optical absorption loss, thereby improves its power output.As shown in drawings, the structure of this class battery comprises that one has the high grade of transparency and the constitutionally stable first floor or substrate 1, electrode 2 before the transparent conductive oxide that on substrate, forms (preceding contact layer), a p layer 5 that constitutes by conducting polymer of the present invention, an i layer 8 that constitutes by the amorphous silicon hydride of non-doping, n layer 9 based on the phosphorus doping of hydrogenated silicon film by utilizing, 22, one metal films 45 of another nesa coating.In this structure, one has replaced traditional p layer based on silicon with the irrelevant fully material of silicon, and successful body plan well behaved amorphous silicon photovoltaic device.

Claims

1. p-i-n type photovoltaic element, it is placed on the preceding contact layer that is made of transparent metal oxide, it is characterized in that:

A) p layer, the p type conduction or the semiconductive polymer film that are not less than 2.2eV by optical band gap constitute;

B) i layer is made of the hydrogenation non crystal silicon film of non-doping, and its thickness is no more than 400 nanometers, is placed on the described p layer;

C) n layer is made of the film based on silane or its alloy of phosphorus doping, is placed on the described i layer;

2. according to the described p-i-n type of claim photovoltaic element, it is characterized in that: between described p layer and described i layer, add a thickness and be no more than the broad-band gap films based on amorphous silicon hydride 5 nanometers, boron doped.

3. according to the described p-i-n type of claim photovoltaic element, it is characterized in that: described p layer is formed by vacuum coating method, and the p type polymer that thickness is no more than 30 nanometers constitutes, and comprises and assembles acetylene and polymerization nitrogen sulfur compound.