Study On Photoelectric Characteristics Of New Absorption Layer In Optics

Thin film solar cells with high conversion efficiency have become a research focus for replacing expensive silicon cells.Copper zinc tin sulfur(CZTS)as a chalcogenide compound,is deemed as a potential absorber material for solar cells.The conversion efficiency of CZTS solar cells is in a bottleneck,and the too wide absorption layer leads to the increase of minority carrier transmission distance and the decrease of conversion efficiency,for breaking through the limitation of traditional thin film cells,a new type of nanowire array absorption layer was prepared by combining the micro-nano structure with the absorption layer of solar cells,and the absorption efficiency of the absorption layer was improved through the light trapping effect.The optical simulation of CZTS absorption layer with nanowire array structure was carried out by FDTD.In the incident light range of 200?1200 nm,when the duty cycle f is 0.6 and the nanowire height h is 2?m,the antireflection effect of the absorption layer was the best.In the experiment,Cu-Zn and Cu-Sn precursor layers were prepared by two step electrodeposition at-1.2 V,600 s and-0.7 V,10 s,and nearly pure CZTS films were prepared by sulfurization annealing at 550?.The ratios of Cu/Zn+Sn and Zn/Sn in the films are 0.82 and 1.25,the optical band gap is 1.52 e V.Then,CZTS nanowire array absorbing layer was prepared by two kinds of templates.Firstly,a dense single layer polystyrene mask was prepared by dropping PS and ethanol solution with the ratio of 1:1.5 and 2 ml SDS surfactant with the mass fraction of 1 wt%.Vertical Si O₂ nanowire substrate was prepared by ICP etching.CZTS nanowire arrays of 2?m and 4?m in height and width were fabricated on the vertical substrate using the process parameters of CZTS thin films,the perpendicularity of nanowires is not ideal,but the size uniformity is good.Then,small size CZTS nanowires with average height and diameter of 450 nm and 100 nm were prepared by using AAO as template,Although the nanowires were broken and lost,the perpendicularity of the nanowire arrays was better.Compared with the CZTS thin film structure,the overall reflectivity loss of the CZTS nanowire arrays in the 0.2?1?m band is reduced by 67%,which improves the absorption efficiency of CZTS absorption layer as a whole.The research on the photoelectric characteristics of the new CZTS nanowire array absorption layer in this project provides a new idea for improving the conversion efficiency of CZTS thin film solar cells.