Wylie Zachery R, Al Katrib Mirella, Campagna Rory, Outen Jonathan E, Smith Samuel, Ruffolo Peter, Bérenguier Baptiste, Bouttemy Muriel, Schulz Philip, Christians Jeffrey A
Department of Engineering, Hope College, Holland, Michigan 49423, United States.
Department of Chemical Engineering, University of Washington, Seattle, Washington 98195, United States.
ACS Energy Lett. 2024 Aug 15;9(9):4378-4385. doi: 10.1021/acsenergylett.4c01465. eCollection 2024 Sep 13.
Halide perovskites are technologically interesting across a wide range of optoelectronic devices, especially photovoltaics, but material stability has proven to be challenging. One degradation mode of note is the meta stability of the perovskite phase of some material compositions. This was studied by tracking the change of CsPbI from its optoelectronically relevant perovskite phase to its thermodynamically stable nonperovskite phase, δ-CsPbI. We explore kinetics as a function of surface chemistry and observe a quantitatively similar, ∼5-fold, reduction in the phase transition rate between neat films and those treated with CsI and CdI. Using XPS to explore surface chemistry changes across samples, we link the reduction in the phase transition rate to the surface iodide concentration. When informed by previous theoretical studies, these experiments point to surface iodide vacancies as the nucleation sites for δ-CsPbI growth and show that phase nucleation is the rate limiting step in δ-CsPbI formation for CsPbI perovskite thin films.
卤化物钙钛矿在广泛的光电器件中具有重要的技术意义，尤其是在光伏领域，但材料稳定性已被证明具有挑战性。一种值得注意的降解模式是某些材料成分的钙钛矿相的亚稳定性。通过追踪CsPbI从其与光电相关的钙钛矿相转变为其热力学稳定的非钙钛矿相δ-CsPbI的变化对此进行了研究。我们探索了作为表面化学函数的动力学，并观察到在纯薄膜与用CsI和CdI处理的薄膜之间，相变速率有相似的定量降低，约为5倍。使用XPS探索样品表面化学变化，我们将相变速率的降低与表面碘化物浓度联系起来。结合先前的理论研究，这些实验表明表面碘化物空位是δ-CsPbI生长的成核位点，并表明相核化是CsPbI钙钛矿薄膜形成δ-CsPbI的速率限制步骤。
