Regulation And Application Of Composite Transparent Conductive Films In Solar Cells

Amorphous silicon?a-Si:H?solar cells are one of the important types of solar cells.A-Si:H solar cells are mainly composed of three kinds of materials:a-Si:H thin films,transparent electrodes and metal electrode materials.Among them,transparent electrode materials are usually transparent conductive oxide?TCO?films,which affect the light loss of the incident light and the collection of photogenerated carriers;a-Si:H thin films impact the absorption coefficients,optical stability and optical band gaps.As a result,optimizing TCOs and a-Si:H films can importantly impact the photoelectric conversion efficiency of a-Si:H solar cells.Aimed at TCOs,the ITO film was first prepared by a thermal reactive evaporation deposition method,and the substrate was heated during the deposition process to better the crystallization of ITO.The material used for the thermal reaction evaporation was an InSn alloy in a ratio of 90%In+10%Sn.During the evaporation process,the deposition rate of ITO was controlled by the evaporation current being65 A,the substrate temperature being 110°C,and the O₂ flow rate being 230 sccm.The ITO?40 nm?films with good crystallinity,average transmittance in visible light range of 87.36%and sheet resistance of 1 k?/sq were obtained.Secondly,three-layer conductive AZO/Ag/AZO?AAA?films with high transmittance?95.8%?and low resistance?6.8?/sq?were fabricated by combining laser pulse deposition?PLD?with magnetron sputtering,and the films were used as front electrodes in CIGS solar cells.Under the irradiation of simulated standard light source environment with AM1.5,the conversion efficiency of the solar cell was 6.3%.Compared with the single-layer AZO?80 nm?CIGS solar cell of the same thickness,the short-circuit current increased from 17.62 mA/cm² to 25.32 mA/cm²,and the efficiency increased by 48%,which can greatly reduce the use of AZO and the production cost.Aimed at a-Si:H solar cells,the intrinsic amorphous silicon absorption layers?i-a-Si:H?with different hydrogen dilutions?R_H?were prepared by Plasma Enhanced Chemical Vapor Deposition?PECVD?method firstly.The effects of hydrogen dilution on the optical band gap,dark conductance and light stability of intrinsic amorphous silicon thin films were investigated.An amorphous silicon solar cell with a band gap being about 1.9 eV was obtained when R_H=5.The other parameters were measured as V_oc=0.875 V,J_sc=15 mA/cm²,FF=66.7%,and E_ff=8.98%.Secondly,in a single-junction amorphous silicon solar cell with FTO as a substrate,the ITO/Ag/ITO three-layer composite conductive film was used as a back-reflectance layer to improve the open circuit voltage and conversion efficiency of the cell.The surface of ITO was treated with CO₂ plasma to create a higher surface energy,which can provide an environment with rich-OH bond and change the growth model of Ag,eventually.Furthermore,Ag/ITO especially sputtered by magnetron was attached to the surface of ITO,which can fabricate the conductive composite film of IAI with 5nm Ag continuous film.The plasma resonance absorption of short-wave light can be reduced by the Ag film,greatly.The average optical transmittance reached 92.7%in the visible light range,and the structure was applied to the back-reflection layer of the amorphous silicon solar cell.The J_scc was increased by 0.5 mA/cm²,the V_occ was increased by 20 mV,and the efficiency was increased to 8.68%.Ag nanowires?Ag NWs?with different dilution concentrations were sprayed on FTO glass substrates to investigate the modulation of the optical transmission of FTO by Ag NWs.The average visible light transmittance of Ag NWs after spraying at a dilution ratio of 1:50 was 73.26%,which was lower than the average transmission of75%by FTO.However,the sample was used as the front TCO layer of amorphous silicon solar cells,and the efficiency was increased by 11.4%and reached to 7.93%,which has a good application prospect.