Reversible Phase Transition for Durable Formamidinium-Dominated Perovskite Photovoltaics,Advanced Materials

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Reversible Phase Transition for Durable Formamidinium-Dominated Perovskite Photovoltaics
Advanced Materials ( IF 27.4 ) Pub Date : 2022-08-10 , DOI: 10.1002/adma.202204458
Huifen Liu ₁ , Nengxu Li ₁ , Zehua Chen _{2,

3} , Shuxia Tao _{2,

3} , Chunlei Li ₄ , Lang Jiang ₄ , Xiuxiu Niu ₅ , Qi Chen ₅ , Feng Wang ₁ , Yu Zhang ₁ , Zijian Huang ₁ , Tinglu Song ₅ , Huanping Zhou ₁

Affiliation

Phase instability is one of the major obstacles to the wide application of formamidinium (FA)-dominated perovskite solar cells (PSCs). An in-depth investigation on relevant phase transitions is urgently needed to explore more effective phase-stabilization strategies. Herein, the reversible phase-transition process of FA₁₋_xCs_xPbI₃ perovskite between photoactive phase (α phase) and non-photoactive phase (δ phase) under humidity, as well as the reversible healing of degraded devices, is monitored. Moreover, through in situ atomic force microscopy, the kinetic transition between α and δ phase is revealed to be the “nucleation–growth transition” process. Density functional theory calculation implies an enthalpy-driven α-to-δ degradation process during humidity aging and an entropy-driven δ-to-α healing process at high temperatures. The α phase of FA₁₋_xCs_xPbI₃ can be stabilized at elevated temperature under high humidity due to the increased nucleation barrier, and the resulting non-encapsulated PSCs retain >90% of their initial efficiency after >1000 h at 60 °C and 60% relative humidity. This finding provides a deepened understanding on the phase-transition process of FA₁₋_xCs_xPbI₃ from both thermodynamics and kinetics points of view, which also presents an effective means to stabilize the α phase of FA-dominated perovskites and devices for practical applications.

中文翻译：

耐用甲脒为主的钙钛矿光伏器件的可逆相变

相位不稳定性是甲脒（FA）主导的钙钛矿太阳能电池（PSC）广泛应用的主要障碍之一。迫切需要对相关相变进行深入研究，以探索更有效的相稳定策略。_{这里，FA 1−}_x Cs _x PbI ₃的可逆相变过程监测湿度下光活性相（α相）和非光活性相（δ相）之间的钙钛矿，以及退化器件的可逆愈合。此外，通过原位原子力显微镜，揭示了α和δ相之间的动力学转变是“成核-生长转变”过程。密度泛函理论计算意味着湿度老化过程中的焓驱动的 α 到 δ 退化过程和高温下的熵驱动的 δ 到 α 愈合过程。_{FA 1−}_x Cs _x PbI ₃的α相由于增加的成核势垒，可以在高温和高湿度下稳定，并且在 60°C 和 60% 的相对湿度下，在 > 1000 小时后，所得的非封装 PSC 保持 > 90% 的初始效率。_{这一发现从热力学和动力学的角度加深了对 FA 1−}_x Cs _x PbI ₃相变过程的理解，也为稳定以 FA 为主的钙钛矿的 α 相和实用器件提供了一种有效的方法。应用程序。

更新日期：2022-08-10

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