Nguyen Linh Lan, Zhang Qiannan, Bradley David G, Xing Zengshan, Salim Teddy, Li Patrick Wen Feng, Mishra Pritish, Mueller Aaron, Mondal Shreyan, Chong Ka Shing, Sum Tze Chien, Hanna John V, Duchamp Martial, Lam Yeng Ming
School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Ave, Singapore 639798, Singapore.
Department of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore.
ACS Nano. 2025 Jun 24;19(24):21927-21941. doi: 10.1021/acsnano.4c10370. Epub 2025 Jun 9.
Although hybrid perovskite-based devices have made significant advances in terms of device performance, long-term stability remains a major challenge to widespread implementation. A unified understanding of the complexity describing the degradation of these types of materials is absent, and in this work, one common hybrid perovskite material, methylammonium lead iodide (MAPI), is used as a vehicle to show how a unified understanding can be achieved using complementary characterization techniques. This work uses low-dose electron microscopes with electric fields ranging from 2.5 to 5 V/μm in a scanning electron microscope before focusing on the lower fields of 1.25 and 2.5 V/μm, where an electric threshold is identified. The results demonstrate that material loss is initiated at the MAPI grain boundaries near the negative electrode interface, where MA is reduced. Above the electrochemical threshold, extensive material volatilization and amorphous layer formation were detected, accompanied by significant PL quenching. High-field solid-state MAS NMR and materials modeling indicate that the MAPI decomposition process is a simultaneous combination of iodine migration, vacancy formation, and organic cation decomposition. The H MAS NMR data from the as-synthesized MAPI show direct evidence of preexisting iodine vacancies that induce the formation of CHNH, forming possible dative coordination to the lead framework positions. Subsequent data from MAPI degraded under exposure to electric fields (1.25 and 2.50 V/μm) directly demonstrate the presence of decomposition products such as NHI, CHI, and CHI through pinhole formation at the electrochemical threshold and more widespread damage induced above this threshold. The methodology presented here can be applied to investigate other hybrid perovskite materials through direct spin coating on the corresponding substrates, deepening our understanding and providing insights for improved device stability.
尽管基于杂化钙钛矿的器件在器件性能方面取得了显著进展，但长期稳定性仍然是广泛应用的主要挑战。目前对于描述这类材料降解的复杂性缺乏统一的认识，在这项工作中，一种常见的杂化钙钛矿材料，甲基碘化铅（MAPI），被用作载体，以展示如何使用互补的表征技术来实现统一的认识。这项工作在聚焦于1.25和2.5 V/μm的较低电场之前，使用了扫描电子显微镜中电场范围为2.5至5 V/μm的低剂量电子显微镜，在该较低电场下确定了一个电阈值。结果表明，材料损失始于靠近负极界面的MAPI晶界处，此处MA被还原。在电化学阈值以上，检测到广泛的材料挥发和非晶层形成，同时伴随着显著的PL猝灭。高场固态MAS NMR和材料建模表明，MAPI分解过程是碘迁移、空位形成和有机阳离子分解的同时结合。来自合成态MAPI的H MAS NMR数据直接证明了预先存在的碘空位的存在，这些空位诱导了CHNH的形成，形成了与铅骨架位置可能的配位。随后来自在电场（1.25和2.50 V/μm）下暴露降解的MAPI的数据直接证明了分解产物的存在，如NHI、CHI和CHI，这是通过在电化学阈值处形成针孔以及在此阈值以上引起的更广泛的损伤而实现的。这里提出的方法可以通过直接旋涂在相应的基板上应用于研究其他杂化钙钛矿材料，加深我们的理解并为提高器件稳定性提供见解。
