CdTe thin film solar cells are the most successful thin film photovoltaic devices in terms of production yield. In the last few years, by changing the original solar cell structure, the efficiency was increased from around 17 % up to 22 %. In particular two main innovations have been introduced: a CdSe_xTe_1-x layer, that narrows the band gap of the absorber near the junction, and a large band gap buffer layer (i.e. Mg_xZn_1-xO). These allow to improve the absorption in the long and in the short wavelength region, respectively. Generally, CdSe_xTe_1-x is formed either by the deposition of a CdSe layer at the junction subsequently mixed with CdTe or by directly depositing a CdSe_xTe_1-x compound, we have instead introduced a different method where CdSe_xTe_1-x is formed by treating a thin CdTe layer at high temperature in selenium atmosphere. The finished device has been fabricated by substituting CdS with SnO₂ and efficiencies exceeding 14 %, with current densities higher than 26 mA/cm² , are obtained by a low substrate temperature process. In this work we analyze and compare our older standard FTO/SnO₂/CdS/CdTe with the novel FTO/SnO₂/CdSe_xTe_1-x/CdTe devices by capacitance voltage, drive level capacitance profiling, and admittance spectroscopy. The results highlight the effect of the selenization process in terms of carrier concentration, carrier profile, and formation of deep and shallow defects. The overall performance of the completed devices is also presented and compared.

CdTe薄膜太阳能电池是产量最高的薄膜光伏器件。最近几年，通过改变原有的太阳能电池结构，效率从17%左右提高到22%。特别是引入了两个主要创新：CdSe _x Te _1-x层，它缩小了结附近吸收体的带隙，以及一个大带隙缓冲层（即 Mg _x Zn _1-x O）。这些允许分别改善长波长区域和短波长区域的吸收。通常，CdSe _x Te _1-x是通过在结处沉积 CdSe 层随后与 CdTe 混合形成的，或者通过直接沉积 CdSe_x Te _1-x化合物，我们引入了一种不同的方法，其中 CdSe _x Te _1-x是通过在硒气氛中高温处理薄 CdTe 层来形成的。成品器件是通过用 SnO ₂代替 CdS 制造的，效率超过 14%，电流密度高于 26 mA/cm ²，是通过低衬底温度工艺获得的。在这项工作中，我们分析并比较了旧标准 FTO/SnO ₂ /CdS/CdTe 与新型 FTO/SnO ₂ /CdSe _x Te _1-x/CdTe 器件通过电容电压、驱动级电容分析和导纳光谱。结果突出了硒化过程在载流子浓度、载流子分布以及深浅缺陷形成方面的影响。还介绍并比较了已完成设备的整体性能。