Study On The Preparation And Performance Optimization For CZTSSe Thin Film Solar Cells

Solar energy is receiving worldwide attention for green and sustainability,solar photovoltaic technology is an effective way to use solar energy.How to use solar energy efficiently and at low cost is the focus of attention.Kesterite Cu₂ZnSn?S,Se?₄?CZTSSe?solar cells have drawn worldwide attention for its prefect photovoltage performance and earth-abundant constituents yet the record efficiency was still lower than its theoretical conversion efficiency?32.2%?.There are many problems that affect the efficiency of the device.Defects at the interface,unfavourable band alignment,and poor film quality of the absorber etc.are all affect the overall performance of the device.In this paper,the crystal quality of the absorber and interface of CZTSSe thin-film solar cells were investigated.The photovoltaic performance of CZTSSe thin-film solar cells with two-step CdS deposition is significantly improved.The main experimental studies are as follows:?1?The CZTSSe film was prepared by solution method,and the effect of selenization conditions on the crystal quality of CZTSSe film was studied.Studies have shown that with the increase of selenization temperature?500°C,520°C and 540°C?and heating rate?90 s,180 s,270 s and 360 s?,the crystallinity of the film first becomes better and then worsens.The CZTSSe film with the best crystal quality was obtained by increasing the temperature from room temperature to 520°C for 10 min in 180 s.The film prepared under this condition was used as the absorber,and the assembled device achieved a photoelectric conversion efficiency of 3.64%.?2?In order to reduce the non-radiative recombination of CZTSSe/CdS interface,we improved the preparation process of CdS layer and obtained a cell device with conversion efficiency of 8.76%by using two-step CdS deposition technology.The devices efficiency of the two-step CdS deposition was 5.12%and 2.03%higher than that of the conventional method and one-step CdS annealing treatment.At the same time,we systematically explored the influence of the first step CdS thickness,annealing time and annealing temperature on the device performance.It was found that the first step of CdS deposition thickness was 20 nm,and after annealing at 200°C for 10 min,the device showed the best photoelectric conversion performance.Tests such as Open-circuit photovoltage decay show that the two-step CdS deposition can improve the crystallinity of the film,and reduce the non-radiative recombination at the interface.At the same time,the possibility of shunt channels formed by direct contact between CZTSSe and ITO is reduced.