A Study On Oxygen Doping Performance Of Intrinsic Layer Of Amorphous Silicon/crystalline Silicon Heterojunction Solar Cells

Amorphous silicon/crystalline silicon heterojunction solar cells（SHJ）are expected to become the mainstream product for future PV technology development due to their high conversion efficiency and high open voltage.Such high conversion efficiency is inseparable from the intrinsic amorphous silicon thin film（passivation layer）in the Solar cell structure,which greatly improves the interface passivation performance.However,the parasitic absorption of the amorphous silicon film itself can lead to a reduction of short-circuit current in the solar cell and thus affect the conversion efficiency.In order to improve the passivation performance and reduce the optical loss.In this paper,the n-α-Si:H film side passivation layer of a c-Si（n）substrate rear-emitter heterojunction solar cell is oxygen-doped by HWCVD（Hot filament chemical vapor deposition）using CO₂as the oxygen source to form an Intrinsic oxygen doped amorphous sillicon thin film（i-α-SiOx:H）to widen the band gap and reduce the optical loss to improve the cell efficiency.The layer was divided into two layers with a thinner i₁and a thicker i₂;the effects of two oxygen-doped structures,i₁layer and（i₁+i₂）bilayer,on the overall passivation layer and solar cell performance were investigated.As well as to study the effect of hot wire current and hydrogen dilution on the performance of the oxygen-doped passivation layer and solar cell based on the optimization of the structure of the oxygen-doped passivation layer;finally,the performance of the film after oxygen doping of the passivation layer on the p-α-Si:H side was initially discussed.The main conclusions are as follows:（1）When the n-α-Si:H film-side passivation layer（i₁）is doped with oxygen,the best overall performance of the film and the highest Solar cell conversion efficiency are achieved when the CO₂flow rate is 4sccm in the coating process;the microstructure factor R of the whole passivation layer is 0.21 at this time;the average cell efficiency（Eff）is 24.16%compared with 23.86%without oxygen doping The efficiency was 0.30%higher with Voc and Jsc of 739.7m V and 39.50m A/cm²respectively than 734.7m V and 39.28m A/cm²of i₁layer without oxygen doping,which were 5m V and 0.22m A/cm²respectively.after light injection annealing boost,Eff were both increased by about 0.17%;reaching 24.33%and 24.03%,respectively.（2）When the（i₁+i₂）bilayer was doped with oxygen,when the CO₂flow control in the coating process was 4sccm for i₁and 8sccm for i₂,respectively;the comprehensive performance of the film was the best and the cell efficiency reached the highest;the microstructure factor R of the whole passivation layer was 0.38 at this time;the average Eff was 24.23%higher than that of 24.16%when only i₁layer was doped with oxygen by 0.07%The efficiency of Voc was 743.9m V,which was 4.2m V higher than that of 739.7m V when only i₁layer was doped with oxygen,and the Jsc was 39.33m A/cm²,which was 0.17m A/cm²lower than that of 39.50m A/cm²when only i₁layer was doped with oxygen;after light injection annealing,the Eff reached24.40%.The comparison of different oxygen doping structures shows that the i₁oxygen doping and（i₁+i₂）oxygen doping have improved Jsc and Voc;however,the improvement in Voc is greater for（i₁+i₂）double-layer oxygen doping than for i₁layer oxygen doping only,and the improvement in Jsc is greater for i₁layer oxygen doping only.（3）The hot wire current and hydrogen dilution have important effects on the thin film and solar cell device.When the hot wire current is 30A,the quali ty of the oxygen doped passivation layer film is the best.At this time,R is 0.33,and Eg reaches its maximum.The film thickness increases with the increas e of current;The battery efficiency reaches a maximum of 24.21%;The efficie ncy of light injection annealing increased by 24.34%.The film quality and pas sivation effect is the best when the hydrogen dilution flow rate is 16sccm,at which time R is 0.28;the film thickness decreases with the increase of hydrog en flow rate;Eff achieves 24.49%high efficiency after light injection annealin g.It was finally determined that when the gas flow ratio of i₁layer of the coa ting process was SiH₄:CO₂:H₂=20sccm:4sccm:0sccm;the gas flow ratio of i₂la yer was SiH₄:CO₂:H₂=20sccm:8sccm:16sccm;the film that device prepared by t he deposited oxygen-doped passivation layer had the best performance when th e hot wire current size was 30A.（4）Oxygen doping of the passivation layer on the side of the p-α-Si:H film leads to a serious decrease in the passivation quality of the film,With the increase in the CO₂flow rate of the coating gas,R also increases,reaching a maximum of 0.56;The minority carrier lifetime decreased from 3461μs without oxygen doping to 727μs at the lowest level.