ZnO多晶薄膜绒面结构及陷光特性分析

Surface morphology and light trapping properties of textured ZnO films

针对当前薄膜太阳电池对光管理的迫切需求,采用磁控溅射及后腐蚀技术制备获得了高性能绒面铝掺杂氧化锌(AZO,ZnO:Al)前电极。深入分析了ZnO多晶薄膜厚度及腐蚀时间对绒面结构及陷光特性的影响。研究结果表明,随多晶薄膜厚度的增加,晶粒尺寸增大,腐蚀后获得的弹坑状表面结构的粒径亦随之增大,绒度增大;随后腐蚀时间的增加,弹坑状粒径及绒度均具有先增大而后趋于饱和的趋势。当沉积ZnO多晶薄膜初始厚达2μm时,获得的薄膜电阻率小于3×10-4Ω·cm,经180s稀HCl(0.5%)腐蚀后,绒面ZnO的均方根粗糙度(RMS)达143nm,400～1 100nm平均透过率达81.4%,在500nm处绒度为84.3%,750nm处绒度可达73.8%,方块电阻小于5Ω/□,满足了硅基薄膜叠层电池对前电极的光电性能需求。

Light trapping technique plays an important role in the high-performance thin film solar cells. In the present study, highly textured ZnO： Al （AZO） films are prepared by medium frequency impulsed magnetron sputtering and wet etching technology which are influenced by film thickness and etching time. The high-quality textured AZO surface is formed by wet etching after the films are deposited by magnetron sputtering technology. The effects of film thickness and etching-time on the textured structure and light-trapping characteristics are investigated. AZO films with different thicknesses are obtained by changing sputtering time, Precise etching time control leads to different textured structure with vari- ous light trapping properties. This textured surface morphology leads to a high haze factor which pro- vides high light trapping efficiency. In addition, the electrical properties of AZO films are also enhanced with higher carrier concentration and mobility as thickness increases. Layers with outstanding electrical （resistivity less than 3×10-4Ω·cm）, optical （average total transmittance higher than 81; from 400 nm to 1 100 nm）,haze （84. 3% and 73. 8; at 500 nm and 750 nm respectively） and morphological （RMS higher than 143 nm,after a 180 s etching process） properties have been obtained, satisfying the demands of photoelectric property of front contact in thin film silicon solar cells and illustrating a good potential application in mass production for large area expansibility.