Stage2沉积速率对低温生长CIGS薄膜特性及器件的影响

摘要

Polycrystalline Cu(In,Ga)Se2 (CIGS) thin ?lms are deposited onto soda-lime glass substrates by the low-temperature three-stage process (below substrate temperature of 420◦C). The influences of growth rate in the second stage on structural and electrical properties of CIGS thin film and device performance are investigated. With the increase of deposition rate during the second stage, the crystallinity and grain compactness of CIGS thin film are promoted, and the double-peak reflection pattern is reduced obviously ,which can reduce the recombination in the grain boundary and help to improve the conversion efficiency of the CIGS solar cell significantly. However, according to the experimental results, higher growth rate during the second stage leads to rough surface and low carrier concentration. The larger surface roughness can be attributed to the larger grain size of secondary-phase Cu2−xSe, and the lower carrier concentration results from the reduction of passivation donor defect effect which is induced by the hindrance of Na diffusion from the glass substrate. High growth rate in the second stage is found to be able to increase the interface recombination and induce shunt paths in the solar cell and then the open circuit voltage and the cell parameters are deteriorated. Finally, a high conversion efficiency of 11.24%is achieved by optimizing the growth rate in the second stage.%　　研究了三步法第二步沉积速率对低温生长Cu(In,Ga)Se2薄膜结构、电学特性和器件特性的影响.通过改变第二步沉积速率发现,提高沉积速率可以显著促进薄膜晶粒生长,提高晶粒紧凑程度降低晶界复合,同时有效改善两相分离现象,提高电池的开路电压和短路电流,有助于Cu(In,Ga)Se2电池光电转换效率的提高.但同时研究表明,随着第二步沉积速率的增加,会促进暂态Cu2−xSe晶粒的生长,引起Cu(In,Ga)Se2薄膜表面粗糙度增大,并阻碍Na向Cu(In,Ga)Se2薄膜表面的扩散,造成施主缺陷钝化效应降低,薄膜载流子浓度下降和电阻率升高,且过高的沉积速率会引起电池内部复合增加并产生分流路径,造成开路电压下降进而引起电池效率恶化.最终,通过最佳化第二步沉积速率,在衬底温度为420◦C时,得到最高转换效率为11.24%的Cu(In,Ga)Se2薄膜太阳电池.