Solution-processed P-Si-based Novel Heterojunction Solar Cells

The advantages of crystalline silicon solar cells in photoelectric conversion efficiency,stability and other aspects make them a leader in the photovoltaic industry and are widely used.Currently,it holds over 90%of the PV market share.Although crystalline silicon solar cells have achieved an ultra-high photoelectric conversion efficiency of 26.81%,high temperature diffusion,plasma enhanced chemical vapor deposition,magnetron sputtering and other complex processes in traditional crystalline silicon solar cells are still the main low cost limiting factors.With the proposal of the concept of dopant-free carrier-selective contact for silicon-based solar cells using metal compounds or organic semiconductor materials,silicon-based heterojunction solar cells can further reduce production costs by optimizing manufacturing processes while maintaining high photoelectric conversion efficiency.Previous studies have shown that solar cells based on PEDOT:PSS and n-Si have made good progress,but there are relatively few reports on the research of low-temperature solution method high-efficiency p-Si-based solar cells.Therefore,this article aims to prepare high-efficiency and low-cost p-Si-based heterojunction solar cells,studying the optimal conditions for solution method deposition of different materials of electron transport layers,and preparing various p-Si-based heterojunction solar cells.Subsequently,detailed research was conducted on the performance optimization of devices with ZnO electron transport layer.The summary of the research content and conclusions conducted is as follows:（1）By spin coating PEDOT:PSS solution on the front side of p-Si and commonly used n-type semiconductor materials（mainly including Sn O₂,ZnO,and Sn S₂）on the back side,novel heterojunction solar cells with PEDOT:PSS/p-Si backcontact structure were prepared under low temperature conditions with a maximum annealing temperature of 135℃in air.The maximum power conversion efficiency of the solar cell reached 8.13%when using Sn S₂with the smallest particle size as electron transport layer under AM 1.5G.The experiment found that the key factor affecting the performance of these backcontact hybrid solar cells is the size of n-type semiconductor nanoparticles,which is essential for the thickness of the electron transport layer of the solar cell.In addition,the material characteristics that the electron transport layer should possess were clarified,which provides valuable reference for subsequent experiments.（2）PEDOT:PSS/p-Si/ZnO backcontact hybrid solar cell was prepared by spin coating ZnO nanoparticles with smaller particle sizes on the back of the silicon wafer.The maximum power photoelectric conversion efficiency of the solar cell measured under AM 1.5G has reached 9.77%.The mechanism of PEDOT:PSS as a hole transport layer and passivation layer has been fully explored here,and the optimal thickness of ZnO as an electron transport layer has been clarified in detail.The preparation process of these solar cells were carried out at low temperatures（no more than 135℃）and high photoelectric conversion efficiency was achieved.（3）Through the study of ZnO electron transport layer in the previous chapter,it was found that the photoelectric conversion efficiency is difficult to further improve only from the dimension of electron transport layer thickness.Considering the energy band bending effect that occurs at the interface after the formation of heterojunction,ZnO material with lower work function than the conduction band bottom of monocrystalline silicon was used,so that they can match the lowest energy level of the conduction band of silicon after the energy band bending.The maximum photoelectric conversion efficiency of the prepared backcontact solar cell measured under AM 1.5G can reach 10.74%.In addition,Nafion doped PEDOT:PSS layer is used to further enhance the passivation ability of organic polymer films.The optimal ratio of Nafion doping was studied,and the photoelectric conversion efficiency of the solar cell was further improved to 11.43%.This is also the highest efficiency reported in current literature for preparing p-Si-based solar cells using solution method,this work provides a useful reference for the preparation of low-cost p-Si-based solar cells.