Copper-bismuth-sulfide (CuBiS) has gained great interest as solar cell absorber owing to the advantages of being cheap, abundant, and non-toxic. Fabrication of phase-pure and large-grain absorbers are desirable for their integration in solar cells. Herein, we have used a sequential evaporation and chalcogenization (350–450 C) process to fabricate phase-pure and large-grain CuBiS films. X-ray diffraction indicated a CuS secondary phase at 350 °C and single-phase CuBiS at 400 and 450 °C in the sulfurized films. Elemental analysis revealed a near-stoichiometric CuBiS composition for all the films. X-ray photoelectron spectroscopy was used to assess the valence states of elements. Microstructural analysis confirmed the formation of compact and large-grained CuBiS films with an average grain size of 5 μm at 350 °C. The grain size decreased with increasing sulfurization temperature (400–450 °C). The direct bandgap decreases from 1.42 eV to 1.32 eV with increasing sulfurization temperature from 350 to 450 °C. Hall measurements indicated decreased electrical resistivity and increased hole mobility and carrier concentration with increasing the sulfurization temperature. From this study, the CuBiS absorbers produced at 400 C exhibited superior phase purity and good quality suitable for the solar cells.

中文翻译：

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薄膜太阳能电池用两阶段工艺制备相纯大晶粒 Cu3BiS3 薄膜

硫化铜铋（CuBiS）作为太阳能电池吸收剂因其廉价、丰富和无毒的优点而引起了人们的极大兴趣。纯相和大颗粒吸收器的制造对于将其集成到太阳能电池中是理想的。在此，我们使用连续蒸发和硫属化（350-450 C）工艺来制造相纯的大晶粒 CuBiS 薄膜。 X 射线衍射表明，硫化膜中在 350 °C 时出现 CuS 第二相，在 400 和 450 °C 时出现单相 CuBiS。元素分析显示所有薄膜均具有接近化学计量的 CuBiS 成分。 X射线光电子能谱用于评估元素的价态。微观结构分析证实在 350 °C 时形成了致密、大晶粒的 CuBiS 薄膜，平均晶粒尺寸为 5 μm。晶粒尺寸随着硫化温度（400-450°C）的升高而减小。随着硫化温度从 350 °C 升高到 450 °C，直接带隙从 1.42 eV 降低到 1.32 eV。霍尔测量表明，随着硫化温度的升高，电阻率降低，空穴迁移率和载流子浓度增加。根据这项研究，在 400 C 下生产的 CuBiS 吸收剂表现出优异的相纯度和适合太阳能电池的良好质量。