Bartesaghi Davide, Slavney Adam H, Gélvez-Rueda María C, Connor Bridget A, Grozema Ferdinand C, Karunadasa Hemamala I, Savenije Tom J
Department of Chemical Engineering, Delft University of Technology, 2628CD Delft, The Netherlands.
Materials Innovation Institute (M2i), 2628CD Delft, The Netherlands.
J Phys Chem C Nanomater Interfaces. 2018 Mar 8;122(9):4809-4816. doi: 10.1021/acs.jpcc.8b00572. Epub 2018 Feb 5.
Double perovskites, comprising two different cations, are potential nontoxic alternatives to lead halide perovskites. Here, we characterized thin films and crystals of CsAgBiBr by time-resolved microwave conductance (TRMC), which probes formation and decay of mobile charges upon pulsed irradiation. Optical excitation of films results in the formation of charges with a yield times mobility product, φΣμ > 1 cm/Vs. On excitation of millimeter-sized crystals, the TRMC signals show, apart from a fast decay, a long-lived tail. Interestingly, this tail is dominant when exciting close to the bandgap, implying the presence of mobile charges with microsecond lifetimes. From the temperature and intensity dependence of the TRMC signals, we deduce a shallow trap state density of around 10/cm in the bulk of the crystal. Despite this high concentration, trap-assisted recombination of charges in the bulk appears to be slow, which is promising for photovoltaic applications.
包含两种不同阳离子的双钙钛矿是卤化铅钙钛矿潜在的无毒替代品。在此，我们通过时间分辨微波电导（TRMC）对CsAgBiBr薄膜和晶体进行了表征，TRMC可探测脉冲辐照后移动电荷的形成和衰减。薄膜的光激发导致形成电荷，其产率与迁移率的乘积φΣμ > 1 cm²/V·s。在毫米尺寸晶体的激发下，TRMC信号除了快速衰减外，还显示出一个长寿命的尾部。有趣的是，当在接近带隙处激发时，这个尾部占主导，这意味着存在寿命为微秒级的移动电荷。从TRMC信号的温度和强度依赖性，我们推断出晶体本体中浅陷阱态密度约为10¹⁸/cm³。尽管该浓度很高，但本体中电荷的陷阱辅助复合似乎很慢，这对于光伏应用来说是很有前景的。
