Understanding Hydrogen Bonding Interactions in Crosslinked Methylammonium Lead Iodide Crystals: Towards Reducing Moisture and Light Degradation Pathways

• Published in: Angewandte Chemie International Edition 2019-09, Vol.58 (39), p.13912-13921
• Main Authors: Nimens, Wendy J., Lefave, Sarah J., Flannery, Laura, Ogle, Jonathan, Smilgies, Detlef‐M., Kieber‐Emmons, Matthew T., Whittaker‐Brooks, Luisa
• Format: Article
• Language: English
• Subjects: Acids; Aging; Chemical bonds; Crosslinking; crystal crosslinking; Crystals; degradation pathways; Hydrogen; Hydrogen bonding; inorganic chemistry; Interfaces; Iodides; Irradiation; Lead; Lead compounds; Light irradiation; materials science; Metal halides; Moisture; Morphology; organic-inorganic hybrid perovskites; Perovskites; Photodegradation; Photovoltaic cells; Solar cells; Stability; Ultraviolet radiation
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201906017

Methylammonium lead halide perovskite‐based solar cells have demonstrated efficiencies as high as 24.2 %, highlighting their potential as inexpensive and solution‐processable alternatives to silicon solar cell technologies. Poor stability towards moisture, ultraviolet irradiation, heat, and a bias voltage of the perovskite layer and its various device interfaces limits the commercial feasibility of this material for outdoor applications. Herein, we investigate the role of hydrogen bonding interactions induced when metal halide perovskite crystals are crosslinked with alkyl or π‐conjugated boronic acid small molecules (‐B(OH)2). The crosslinked perovskite crystals are investigated under continuous light irradiation and moisture exposure. These studies demonstrate that the origin of the interaction between the alkyl or π‐conjugated crosslinking molecules is due to hydrogen bonding between the ‐B(OH)2 terminal group of the crosslinker and the I of the [PbI6]4− octahedra of the perovskite layer. Also, this interaction influences the stability of the perovskite layer towards moisture and ultraviolet light irradiation. Morphology and structural analyses, as well as IR studies as a function of aging under both dark and light conditions show that π‐conjugated boronic acid molecules are more effective crosslinkers of the perovskite crystals than their alkyl counterparts thus imparting better stability towards light and moisture degradation. Crosslinked perovskite crystals: Incorporation of π‐conjugated organic crosslinkers into the organic‐inorganic hybrid perovskite structure imparts stability towards light and high moisture degradation without compromising power conversion efficiencies.