一步法电化学沉积Cu(In1-x,Gax)Se2薄膜的特性

在CuCl2、InCl3、GaCl3及H2SeO3组成的酸性水溶液电沉积体系中, 对Mo/玻璃衬底上一步法电沉积Cu(In1-x, Gax)Se2(简写为CIGS)薄膜进行了研究. 为了稳定溶液的化学性质, 在溶液中加入邻苯二甲酸氢钾和氨基磺酸作为pH缓冲剂, 将溶液的pH值控制在约2.5, 并提高薄膜中Ga的含量. 通过大量实验优化了溶液组成及电沉积条件, 得到接近化学计量比贫Cu 的CIGS薄膜(当Cu与In+Ga的摩尔比为1时, 称为符合化学计量比的CIGS薄膜; 当其比值为0.8-1时, 称为贫Cu或富In的CIGS 薄膜)预置层, 薄膜表面光亮、致密、无裂纹. 利用循环伏安法初步研究了一步法电沉积CIGS薄膜的反应机理, 在沉积过程中, Se4+离子先还原生成单质Se, 再诱导Cu2+、Ga3+和In3+发生共沉积. 电沉积CIGS薄膜预置层在固态硒源280 ℃蒸发的硒气氛中进行硒化再结晶, 有效改善了薄膜的结晶结构, 且成份基本不发生变化,但是表面会产生大量的裂纹.

Properties of One-Step Electrodeposited Cu(In1-x,Gax)Se2 Thin Films

One-step electrodeposition(ED) of Cu(In1-x, Gax)Se2 (CIGS) thin films on Mo/glass substrates from aqueous solutions containing CuCl2, InCl3, GaCl3, and H2SeO3 was studied. In order to stabilize the solutions, they were buffered using a potassium biphthalate/sulfamic acid mixture giving a bath of pH 2.5. The type of the solutions would influence Ga concentration in the CIGS films. In general, CIGS thin film is called stoichiometric compound when the molar ratio of Cu to In+Ga is 1, and when the ratio is in the range of 0.8-1, it is called near stoichiometric and slightly Cu-poor or In-rich CIGS compound. As-deposited films were near stoichiometric and slightly Cu-poor CIGS precursors with smooth, compact, crack-free surface by the optimization of the solution composition and the deposition condition. The electrodeposition mechanisms of CIGS on Mo substrates were studied by cyclic voltammetry. The results showed that Se4+ was first reduced to Se, and then Cu2+, In3 +, and Ga3+ were deposited via the induced co- deposition mechanism at more positive potentials than they were reduced. As-deposited films were selenized and recrystallized at 550 ℃ in Se vapor with a Se source temperature of 280 ℃, which improved crystal structure of the films and changed little the compositions of ED-CIGS thin films, but resulted in cracking of the films.