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Chemical and Structural Degradation of CH 3 NH 3 PbI 3 Propagate from PEDOT:PSS Interface in the Presence of Humidity
Author(s) -
Thomas Sara A.,
Hamill Jr J. Clay,
White Sarah Jane O.,
Loo YuehLin
Publication year - 2021
Publication title -
advanced materials interfaces
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.671
H-Index - 65
ISSN - 2196-7350
DOI - 10.1002/admi.202100505
Subject(s) - perovskite (structure) , materials science , tetragonal crystal system , pedot:pss , iodide , relative humidity , solubility , phase (matter) , crystallography , analytical chemistry (journal) , crystal structure , nanotechnology , inorganic chemistry , layer (electronics) , chemistry , organic chemistry , physics , thermodynamics
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 (CH 3 NH 3 PbI 3 ) 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 (CH 3 ) 2 NH 2 PbI 3 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, (CH 3 ) 2 NH 2 + . The partial A‐site substitution of CH 3 NH 3 + for (CH 3 ) 2 NH 2 + to produce a cubic (CH 3 NH 3 ) 1− x [(CH 3 ) 2 NH 2 ] x PbI 3 phase explains the structural change from tetragonal to cubic during short‐term humidity exposure. When (CH 3 ) 2 NH 2 + content exceeds its solubility limit in the perovskite during longer humidity exposures, a (CH 3 ) 2 NH 2 + ‐rich, hexagonal phase of (CH 3 NH 3 ) 1− x [(CH 3 ) 2 NH 2 ] x PbI 3 emerges. These interfacial interactions may have consequences for device stability and performance beyond CH 3 NH 3 PbI 3 model systems and merit close attention from the perovskite research community.