Zhang Xianfeng, Wu Hongde, Fu Engang, Wang Yuehui
Zhongshan Institute, University of Electronic Science and Technology of China, Zhongshan 528402, China.
State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871, China.
Nanomaterials (Basel). 2019 Jun 5;9(6):855. doi: 10.3390/nano9060855.
Secondary phases are common in CuZnSnS (CZTS) thin films, which can be fatal to the performance of solar cell devices fabricated from this material. They are difficult to detect by X-Ray diffraction (XRD) because of the weak peak in spectra compared with the CZTS layer. Herein, it was found that in-depth elemental distribution by a secondary ion mass spectroscopy method illustrated uniform film composition in the bulk with slight fluctuation between different grains. X-ray photoelectron spectroscopy (XPS) measurement was conducted after sputtering the layer with different depths. An Auger electron spectrum with Auger parameter were used to check the chemical states of elements and examine the distribution of secondary phases in the CZTS films. Secondary phases of CuS, ZnS and SnS were detected at the surface of the CZTS film within a 50-nm thickness while no secondary phases were discovered in the bulk. The solar cell fabricated with the as-grown CZTS films showed a conversion efficiency of 2.1% (: 514.3 mV, : 10.4 mA/cm, : 39.3%) with an area of 0.2 cm under a 100 mW/cm illumination. After a 50-nm sputtering on the CZTS film, the conversion efficiency of the solar cell was improved to 6.2% (: 634.0 mV, : 17.3 mA/cm, : 56.9%).
第二相在CuZnSnS（CZTS）薄膜中很常见，这对于用这种材料制造的太阳能电池器件的性能可能是致命的。由于与CZTS层相比光谱中的峰较弱，它们很难通过X射线衍射（XRD）检测到。在此，发现通过二次离子质谱法进行的深度元素分布表明，整体薄膜成分均匀，不同晶粒之间存在轻微波动。在对该层进行不同深度的溅射后进行了X射线光电子能谱（XPS）测量。利用带有俄歇参数的俄歇电子能谱来检查元素的化学状态，并研究CZTS薄膜中第二相的分布。在厚度为50纳米的CZTS薄膜表面检测到了CuS、ZnS和SnS的第二相，而在整体中未发现第二相。用生长态的CZTS薄膜制造的太阳能电池在100 mW/cm的光照下，面积为0.2平方厘米时，显示出2.1%的转换效率（开路电压：514.3 mV，短路电流密度：10.4 mA/cm，填充因子：39.3%）。在CZTS薄膜上进行50纳米的溅射后，太阳能电池的转换效率提高到了6.2%（开路电压：634.0 mV，短路电流密度：17.3 mA/cm，填充因子：56.9%）。
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