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Chemical and structural degradation of CH3NH3PbI3 propagate from PEDOT:PSS interface in the presence of humidity

July 27, 2021

Understanding interfacial reactions that occur between the active layer and charge-transport layers can extend the stability of perovskite solar cells. In this study, the exposure of methylammonium lead iodide (CH3NH3PbI3) thin films prepared on poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)-coated glass to 70% relative humidity (R.H.) leads to a perovskite crystal structure change from tetragonal to cubic within 2 days. Interface-sensitive photoluminescence measurements indicate that the structural change originates at the PEDOT:PSS/perovskite interface. During exposure to 30% R.H., the same structural change occurs over a much longer time scale (>200 days), and a reflection consistent with the presence of (CH3)2NH2PbI3 is detected to coexist with the cubic phase by X-ray diffraction pattern. The authors propose that chemical interactions at the PEDOT:PSS/perovskite interface, facilitated by humidity, promote the formation of dimethylammonium, (CH3)2NH2+. The partial A-site substitution of CH3NH3+ for (CH3)2NH2+ to produce a cubic (CH3NH3)1−x[(CH3)2NH2]xPbI3 phase explains the structural change from tetragonal to cubic during short-term humidity exposure. When (CH3)2NH2+ content exceeds its solubility limit in the perovskite during longer humidity exposures, a (CH3)2NH2+-rich, hexagonal phase of (CH3NH3)1−x[(CH3)2NH2]xPbI3 emerges. These interfacial interactions may have consequences for device stability and performance beyond CH3NH3PbI3 model systems and merit close attention from the perovskite research community.

Citation Information

Publication Year 2021
Title Chemical and structural degradation of CH3NH3PbI3 propagate from PEDOT:PSS interface in the presence of humidity
DOI https://doi.org/10.1002/admi.202100505
Authors Sara A Thomas, J. Clay Hamill Jr, Sarah Jane White, Yueh-Lin Loo
Publication Type Article
Publication Subtype Journal Article
Series Title Advanced Materials Interfaces
Index ID 70226198
Record Source USGS Publications Warehouse
USGS Organization Eastern Mineral and Environmental Resources Science Center; Geology, Energy & Minerals Science Center