Bismuth triiodide (BiI3) has been studied in recent years with the aim of developing lead-free semiconductors for photovoltaics. It has also appeared in X-ray detectors due to the high density of the Bismuth element. This material is attractive as an active layer in solar cells, or may be feasible for conversion into perovskite-like material (MA3Bi2I9), being also suitable for photovoltaic applications. In this study, we report on the thermomechanical properties (stress, hardness, coefficient of thermal expansion, and biaxial and reduced Young’s moduli) of BiI3 thin films deposited by thermal evaporation. The stress was determined as a function of temperature, adopting the thermally induced bending technique, which allowed us to extract the coefficient of thermal expansion (31 × 10−6 °C−1) and Young’s biaxial modulus (19.6 GPa) for the films. Nanohardness (~0.76 GPa) and a reduced Young’s modulus of 27.1 GPa were determined through nanoindentation measurements.
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机译：近年来已经研究了三碘化铋（BiI3），其目的是开发用于光伏的无铅半导体。由于铋元素的高密度，它也出现在X射线探测器中。这种材料作为太阳能电池中的活性层具有吸引力，或者对于转换成钙钛矿型材料（MA3Bi2I9）也是可行的，也适用于光伏应用。在这项研究中，我们报告了通过热蒸发沉积的BiI3薄膜的热机械性能（应力，硬度，热膨胀系数以及双轴和降低的杨氏模量）。采用热诱导弯曲技术确定应力随温度的变化，这使我们能够提取热膨胀系数（31×10 -6 °C -1 ）和薄膜的杨氏双轴模量（19.6 GPa）。通过纳米压痕测量确定了纳米硬度（〜0.76 GPa）和降低的杨氏模量27.1 GPa。
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