双梯度带隙铜铟镓硒光伏薄膜的光电化学沉积机理及其性能研究

Photoelectrochemical deposition of photovoltaic copper indium gallium selenide (CIGS) thin films is presented in this project, which aims at solving the problems in traditional electrodeposition such as the difficulty in incorporation of ⅢA group elements, generation of secondary phases, incapability in band gap gradients, poor morphology, and the low deposition rate. Efforts will be devoted to revealing the characteristics of mass and charge transfer in deposition process via the contruction and analysis on semiconductor/electrolyte energy level structure and equivalent circuit. Besides, relevant electrochemical behaviors will be explored using cyclic voltammetry and electrochemical quartz crystal microbalance technology, and the growth mechanism of deposited film can be induced from a combination of chronoamperometry and evolving law research on the film morphology, composition and phases. Furthermore, through film characterization, the effects of illumination on the deposition rate, film morphology, incorporation of ⅢA group elements, and secondary phases will be confirmed. Concurrently, the influence of process parameters on the film properties is also investigated, based on which one can determine the optimized parameters. In addition, controlled double gradient distribution of the band gap is realizable with rational design of the illumination schedule,the relationship among which and photoelectric conversion performances can be established to obtian the best double gradient distribution and means of its achieving. Consequently, this project is of great significance in promoting the electrochemical deposition technology of CIGS thin film, and further motivating the low-cost production and large-scale application of CIGS thin film solar cells.

本项目提出采用光电化学沉积法制备铜铟镓硒（CIGS）光伏薄膜,以解决传统电化学沉积存在的ⅢA族元素并入难、二次相易生成、带隙梯度化难、形貌差和沉积速率慢等不足。项目将结合半导体/电解液能级结构和等效电路的构建分析，揭示沉积的传质传荷特征；采用循环伏安和电化学石英晶体微天平技术探明沉积电化学行为，并通过薄膜形貌、成分和物相的时间演变规律研究及计时安培分析，归纳薄膜的形成与生长机制。通过对薄膜的表征分析，明确光照对沉积速率、形貌、ⅢA族元素并入和二次相影响的规律及机制，同时考察各沉积工艺参数对薄膜物化性质的影响，确定优化的沉积工艺参数范围。通过光照制度设计实现带隙的双梯度可控分布，建立光照制度、双梯度分布和光电转换性能之间的关系，获得最优的双梯度分布及其实现手段。本项目的开展可有效促进CIGS薄膜电化学沉积技术的进步，推动CIGS薄膜太阳电池的低成本制造和规模应用。

铜铟镓硒薄膜太阳电池被认为是最重要和最具发展前景的光伏电池之一，电化学沉积法是一种有产业化前景的CIGS 薄膜制备方法，但存在难以实现薄膜高速高质量沉积、难以实现Ga 并入途径的有效控制和难以实现CIGS 薄膜Ga/(In+Ga)的梯度分布等问题。本项目提出采用光电化学沉积法制备铜铟镓硒（CIGS）光伏薄膜,以解决传统电化学沉积存在的不足。本项目建立了以铜铟镓硒为代表的金属硒化物的电沉积热力学与动力学基本理论，并在此基础上开展了了光电化学沉积法制备梯度带隙铜铟镓硒薄膜的研究，揭示了电沉积Cu(In,Ga)Se2薄膜时In和Ga的并入途径、络合剂氨基磺酸钠的作用机制以及光电化学沉积工艺参数对沉积薄膜性能的影响规律，发现光照可以有效提高难沉积元素In和Ga的并入，并可通过改变光强获得对Ga/(In+Ga)纵向分布的控制，实现Ga/(In+Ga)和带隙宽度的双梯度分布。优化建立了光电化学沉积铜铟镓硒薄膜的工艺，并研究了铜铟镓硒的热处理、钾掺杂和刻蚀工艺，形成了基于光电化学沉积铜铟镓硒薄膜的技术原型。制备出面积为41.848 mm2铜铟镓硒薄膜太阳电池短路电流密度为32.74mA/cm2，开路电压为630mV，填充因子为0.717，其光电转换效率达14.8%（经中国计量科学研究院第三方测量）。此外，还开发了新型无铟铜锌锡硫（CZTS）薄膜太阳电池，通过钾掺杂、低压退火和硒化等手段，使得基于溶胶凝胶法制备CZTS太阳电池的光电转换效率达到8.2%，基于电沉积的CZTS太阳电池的光电转换效率达到4.2%。该项目基于光电化学沉积建立了一种新的铜铟镓硒薄膜沉积方法，并阐明了沉积机理，对加深对铜铟镓硒材料的认识和促进铜铟镓硒薄膜制备技术的进步具有重要意义。同时开展的铜锌锡硫薄膜太阳电池研究也为解决铜铟镓硒存在使用稀散元素的问题提供了新的思路和途径。基于上述工作，发表SCI论文18篇，申报专利4项，协助培养博士生6名，硕士生6名。