Wu Junsheng, Fang Fang, Zhao Zhuo, Li Tong, Ullah Rizwan, Lv Zhe, Zhou Yanwen, Sawtell David
School of Chemical Engineering, University of Science and Technology Liaoning 114051 Liaoning Anshan China.
Institute of Surface Engineering, University of Science and Technology Liaoning Anshan 114051 Liaoning China
RSC Adv. 2019 Nov 13;9(63):37119-37126. doi: 10.1039/c9ra07415e. eCollection 2019 Nov 11.
To study the effect of fluorine ions on the phase transformation of a tin-based perovskite, CsSnI (F) films were deposited by using thermal vacuum evaporation from a mixed powder of SnI, SnF and CsI, followed by rapid vacuum annealing. The color evolution, structure, and properties of CsSnI F films aged in air were observed and analyzed. The results showed that the colors of the films changed from black to yellow, and finally presented as black again over time; the unstable B-γ-CsSnI F phase transformed into the Y-CsSnI F phase, which is then recombined into the CsSnI F phase with the generation of SnO in air. Fluorine dopant inhibited the oxidation process. The postponement of the phase transformation is due to the stronger bonds between F and Sn than that between I and Sn. The color changing process of the CsSnI F films slowed that the hole concentrations increased and the resistivities decreased with the increase of the F dopant ratio. With the addition of SnF, light harvesting within the visible light region was significantly enhanced. Comparison of the optical and electrical properties of the fresh annealed CsSnI F films showed that the band gaps of the aged films widened, the hole concentrations kept the same order, the hole mobilities reduced and therefore, the resistivities increased. The double layer CsSnI F phase also showed 'p' type semi-conductor properties, which might be due to the incomplete transition of Sn to Sn, Sn provides holes as the acceptor.
为研究氟离子对锡基钙钛矿CsSnI₃(F)薄膜相变的影响，采用热真空蒸发法从SnI₂、SnF₂和CsI的混合粉末中沉积CsSnI₃(F)薄膜，随后进行快速真空退火。观察并分析了在空气中老化的CsSnI₃(F)薄膜的颜色演变、结构和性能。结果表明，薄膜颜色随时间从黑色变为黄色，最终又变回黑色；不稳定的B-γ-CsSnI₃(F)相转变为Y-CsSnI₃(F)相，然后在空气中重新组合成CsSnI₃(F)相并生成SnO。氟掺杂剂抑制了氧化过程。相变的延迟是由于F与Sn之间的键比I与Sn之间的键更强。CsSnI₃(F)薄膜的颜色变化过程表明，随着F掺杂比例的增加，空穴浓度增加，电阻率降低。添加SnF₂后，可见光区域的光捕获显著增强。新鲜退火的CsSnI₃(F)薄膜与老化薄膜的光学和电学性能比较表明，老化薄膜的带隙变宽，空穴浓度保持相同顺序，空穴迁移率降低，因此电阻率增加。双层CsSnI₃(F)相也表现出“p”型半导体特性，这可能是由于Sn向Sn²⁺的不完全转变，Sn作为受主提供空穴。
