Sadoughi Golnaz, Starr David E, Handick Evelyn, Stranks Samuel D, Gorgoi Mihaela, Wilks Regan G, Bär Marcus, Snaith Henry J
†Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom.
‡Renewable Energy, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin, Germany.
ACS Appl Mater Interfaces. 2015 Jun 24;7(24):13440-4. doi: 10.1021/acsami.5b02237. Epub 2015 Jun 10.
We have employed soft and hard X-ray photoelectron spectroscopies to study the depth-dependent chemical composition of mixed-halide perovskite thin films used in high-performance solar cells. We detect substantial amounts of metallic lead in the perovskite films, which correlate with significant density of states above the valence band maximum. The metallic lead content is higher in the bulk of the perovskite films than at the surface. Using an optimized postanneal process in air, we can reduce the metallic lead content in the perovskite film. This process reduces the amount of metallic lead and a corresponding increase in the photoluminescence quantum efficiency of the perovskite films can be observed. This correlation indicates that metallic lead impurities are likely a key defect whose concentration can be controlled by simple annealing procedures in order to increase the performance for perovskite solar cells.
我们采用软X射线和硬X射线光电子能谱来研究用于高性能太阳能电池的混合卤化物钙钛矿薄膜随深度变化的化学成分。我们在钙钛矿薄膜中检测到大量金属铅，这与价带最大值以上显著的态密度相关。钙钛矿薄膜 bulk 中的金属铅含量高于表面。通过在空气中使用优化的后退火工艺，我们可以降低钙钛矿薄膜中的金属铅含量。此工艺减少了金属铅的量，并且可以观察到钙钛矿薄膜的光致发光量子效率相应提高。这种相关性表明，金属铅杂质可能是一个关键缺陷，其浓度可以通过简单的退火程序来控制，以提高钙钛矿太阳能电池的性能。
