Gunasekaran Rajendra Kumar, Chinnadurai Deviprasath, Selvaraj Aravindha Raja, Rajendiran Rajmohan, Senthil Karuppanan, Prabakar Kandasamy
Department of Electrical and Computer Engineering, Pusan National University, San 30, Jangjeong-Dong, Gumjeong-Ku, Busan-, 46241, South Korea.
Department of Physics, Bannari Amman Institute of Technology, Sathyamangalam, 638 401, Tamil Nadu, India.
Chemphyschem. 2018 Jun 19;19(12):1507-1513. doi: 10.1002/cphc.201800002. Epub 2018 Apr 14.
Organic-inorganic lead halide perovskite phases segregate (and their structures degrade) under illumination, exhibiting a poor stability with hysteresis and producing halide accumulation at the surface.In this work, we observed structural and interfacial dissociation in methylammonium lead iodide (CH NH PbI ) perovskites even under dark and vacuum conditions. Here, we investigate the origin and consequences of self-degradation in CH NH PbI perovskites stored in the dark under vacuum. Diffraction and photoelectron spectroscopic studies reveal the structural dissociation of perovskites into PbI , which further dissociates into metallic lead (Pb ) and I ions, collectively degrading the perovskite stability. Using TOF-SIMS analysis, AuI formation was directly observed, and it was found that an interplay between CH NH , I , and mobile I ions continuously regenerates more I ions, which diffuse to the surface even in the absence of light. Besides, halide diffusion causes a concentration gradient between Pb and I and creates other ionic traps (PbI , PbI ) that segregate as clusters at the perovskite/gold interface. A shift of the onset of the absorption band edge towards shorter wavelengths was also observed by absorption spectroscopy, indicating the formation of defect species upon aging in the dark under vacuum.
有机-无机卤化铅钙钛矿相在光照下会发生分离（且其结构会降解），表现出较差的稳定性并伴有滞后现象，同时在表面产生卤化物积累。在这项工作中，我们观察到即使在黑暗和真空条件下，甲基碘化铅（CH₃NH₃PbI₃）钙钛矿中也存在结构和界面解离现象。在此，我们研究了在真空黑暗条件下储存的CH₃NH₃PbI₃钙钛矿自降解的起源和后果。衍射和光电子能谱研究表明，钙钛矿结构解离为PbI₂，PbI₂进一步解离为金属铅（Pb）和I⁻离子，共同降低了钙钛矿的稳定性。通过飞行时间二次离子质谱（TOF-SIMS）分析，直接观察到了AuI的形成，并且发现CH₃NH₃⁺、I⁻和可移动的I⁻离子之间的相互作用不断再生出更多的I⁻离子，即使在没有光照的情况下，这些离子也会扩散到表面。此外，卤化物扩散导致Pb和I之间形成浓度梯度，并产生其他离子陷阱（PbI₂、PbI₃），这些陷阱以团簇形式在钙钛矿/金界面处分离。通过吸收光谱还观察到吸收带边缘的起始位置向较短波长移动，这表明在真空黑暗条件下老化时会形成缺陷物种。
