本文采用溶液法制备铜锌锡硒(Cu2ZnSnSe4, CZTSe)薄膜。通过在溶液中加入少量的锗(Ge), 探究Ge的引入对CZTSe薄膜及其器件性能的影响。为了对比分析, 分别制备了不含Ge的CZTSe和含少量Ge的铜锌锡锗硒［Cu2Zn(Sn, Ge)Se4, CZTGSe］两组薄膜及其薄膜太阳电池。分别利用X射线衍射仪(XRD)、拉曼(Raman)光谱、扫描电子显微镜(SEM)、霍尔(Hall)测试、电流-电压(J-V)曲线和外量子效率(EQE)测试等手段对吸收层薄膜的晶体结构、相的纯度、表面形貌、载流子浓度, 以及完整器件的电学性能进行表征和分析。结果表明, 在CZTSe薄膜中引入少量Ge可以与Se形成液体流动剂, 提升吸收层薄膜结晶度, 改善晶体质量, 减少晶界数量, 降低光生载流子在晶界处的复合, 提高载流子寿命。此外, Ge对Sn的部分取代可以降低与Sn有关的缺陷态密度, 增加带隙, 提高开路电压, 同时改善串联电阻和并联电阻, 提高填充因子。最终获得了开路电压为513.2 mV、短路电流为27.47 mA/cm2、填充因子为62.68%、光电转换效率为8.83%的CZTGSe薄膜太阳电池。

In this paper, Cu2ZnSnSe4(CZTSe) thin films were prepared by solution method. A small amount of Ge was added into the solution and the effect of Ge incorporation on the properties of CZTSe thin films and devices was investigated. For comparison, two sets of CZTSe thin films and corresponding solar cells, namely CZTSe without Ge and CZTSe with a small amount of Ge［Cu2Zn(Sn, Ge)Se4, CZTGSe］were prepared. The crystal structure, phase purity, surface morphology, and carrier concentration of the prepared thin films, as well as the electrical properties of the complete devices were characterized and analyzed by X-ray diffractometer (XRD), Raman spectra, scanning electron microscopy (SEM), Hall measure system, current voltage (J-V) curve, and external quantum efficiency (EQE) tests, respectively. The results demonstrate that Ge incorporation into the CZTSe film promotes the crystallization mainly due to the formation of Ge-Se liquid flux during the selenization process, reduces the number of grain boundaries and the minority carriers recombination at the grain boundaries and enhances the carrier lifetime. In addition, partial substitution of Ge for Sn reduces the density of defect states associated with Sn, increases the energy band gap and open circuit voltage, improves the series and parallel resistance, and thus increases the fill factor. Finally, the prepared CZTGSe thin film solar cells reach a photoelectric conversion efficiency of 8.83% with open circuit voltage of 513.2 mV, short circuit current of 27.47 mA/cm2 and fill factor of 62.68%.