Fu Xiao, Jacobs Daniel A, Beck Fiona J, Duong The, Shen Heping, Catchpole Kylie R, White Thomas P
Centre for Sustainable Energy Systems, Research School of Engineering, Australian National University, Canberra, 2601 Australia.
Phys Chem Chem Phys. 2016 Aug 10;18(32):22557-64. doi: 10.1039/c6cp03779h.
Organometal halide perovskite-based solar cells have rapidly achieved high efficiency in recent years. However, many fundamental recombination mechanisms underlying the excellent performance are still not well understood. Here we apply confocal photoluminescence microscopy to investigate the time and spatial characteristics of light-induced trap de-activation in CH3NH3PbI3 perovskite films. Trap de-activation is characterized by a dramatic increase in PL emission during continuous laser illumination accompanied by a lateral expansion of the PL enhancement far beyond the laser spot. These observations are attributed to an oxygen-assisted trap de-activation process associated with carrier diffusion. To model this effect, we add a trap de-activation term to the standard semiconductor carrier recombination and diffusion models. With this approach we are able to reproduce the observed temporal and spatial dependence of laser induced PL enhancement using realistic physical parameters. Furthermore, we experimentally investigate the role of trap diffusion in this process, and demonstrate that the trap de-activation is not permanent, with the traps appearing again once the illumination is turned off. This study provides new insights into recombination and trap dynamics in perovskite films that could offer a better understanding of perovskite solar cell performance.
近年来，基于有机金属卤化物钙钛矿的太阳能电池迅速实现了高效率。然而，许多支撑其优异性能的基本复合机制仍未得到很好的理解。在此，我们应用共聚焦光致发光显微镜来研究CH3NH3PbI3钙钛矿薄膜中光诱导陷阱去激活的时间和空间特性。陷阱去激活的特征是在连续激光照射期间光致发光（PL）发射急剧增加，同时PL增强的横向扩展远远超出激光光斑。这些观察结果归因于与载流子扩散相关的氧辅助陷阱去激活过程。为了对这种效应进行建模，我们在标准半导体载流子复合和扩散模型中添加了一个陷阱去激活项。通过这种方法，我们能够使用实际的物理参数重现观察到的激光诱导PL增强的时间和空间依赖性。此外，我们通过实验研究了陷阱扩散在此过程中的作用，并证明陷阱去激活不是永久性的，一旦光照关闭，陷阱会再次出现。这项研究为钙钛矿薄膜中的复合和陷阱动力学提供了新的见解，有助于更好地理解钙钛矿太阳能电池的性能。
