Funk Hannah, Shargaieva Oleksandra, Eljarrat Alberto, Unger Eva L, Koch Christoph T, Abou-Ras Daniel
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin, Germany.
Structure and Dynamics of Energy Materials, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin, Germany.
J Phys Chem Lett. 2020 Jul 2;11(13):4945-4950. doi: 10.1021/acs.jpclett.0c01296. Epub 2020 Jun 10.
Photoinduced phase separation, which limits the available band gap energies for photovoltaic applications, was reported for a range of mixed-halide perovskites. A microscopic understanding of the phase separation mechanism is still lacking but may be beneficial to rationalize limitations as well as enable the design of phase-stable perovskite semiconductors. In this letter, electron-beam-induced phase separations and transformations were investigated in a small crystallite of CsPb(BrI) by means of in situ high-resolution imaging in a transmission electron microscope. The acquired time series was evaluated using principal and independent component analysis to classify the structural change during the illumination by the electron beam. A more iodine-rich phase with the approximate composition of CsPb(BrI) was found to form at the edges of the particle, while a ternary pure bromide phase of CsPbBr remained at its center. These results provide an atomistic picture of in-grain phase segregation into iodide-rich phases at grain boundaries and bromide-rich phases in the interior of the grain.
据报道，一系列混合卤化物钙钛矿存在光致相分离现象，这限制了光伏应用中可用的带隙能量。目前仍缺乏对相分离机制的微观理解，但这可能有助于解释相关限制，并推动相稳定钙钛矿半导体的设计。在这封信中，通过透射电子显微镜中的原位高分辨率成像，研究了CsPb(BrI)微晶中的电子束诱导相分离和转变。利用主成分分析和独立成分分析对采集到的时间序列进行评估，以对电子束照射期间的结构变化进行分类。发现在颗粒边缘形成了一种碘含量更高、近似组成为CsPb(BrI)的相，而颗粒中心则保留了CsPbBr的三元纯溴化物相。这些结果提供了一幅晶粒内相分离的原子图像，即在晶界处形成富碘相，在晶粒内部形成富溴相。
