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.P oor stability towards moisture,u ltraviolet irradiation, heat, and ab ias 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 p-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 alkylorp-conjugated crosslinking molecules is due to hydrogen bonding between the -B(OH) 2 terminal group of the crosslinker and the Io ft he [PbI 6 ] 4À octahedra of the perovskite layer.A lso,t his interaction influences the stability of the perovskite layer towards moisture and ultraviolet light irradiation. Morphology and structural analyses,aswell as IR studies as afunction of aging under both dark and light conditions showthat p-conjugated boronic acid molecules are more effective crosslinkers of the perovskite crystals than their alkylc ounterparts thus imparting better stability towards light and moisture degradation.
Perovskites based on methylammonium lead halides, CH 3 NH 3 PbX 3 (X = Cl, Br, I), have emerged as one of the most promising materials in solar cell technology. Although the photovoltaics field has witnessed significant progress in the power conversion efficiency (PCE) of perovskite solar cells, unveiling the contribution of the various factors (i.e., energy level alignment, trap states, electron (hole) mobility, interface interactions, and morphology) affecting the observed PCEs is extremely crucial to achieve reproducible and stable devices. This work aims to understand charge transport and recombination within conventional perovskite solar cells due to modifications of the morphology, optoelectronic properties, and energy levels of the titania electron transport layer. Here, we utilize two different processing methods (i.e., solution and sputtering depositions) to yield three morphologically different titania electron transport layers (i.e., planar bulk TiO 2 , mesoporous TiO x , and sputtered TiO 2 ). We find that the most important factors affecting the PCEs in perovskite solar cells are related to trap-assisted recombination and energy level alignment due to variations in the electron transport layer/perovskite interface. Similarly, we observe that morphologies of both the electron transport layer and the perovskite active layer play a minor role on the observed PCEs.
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