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

Abstract

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.

How machine learning can help select capping layers to suppress perovskite degradation

“…10 ) 43 . This evidence might support the hypothesis that hydrogen bonding plays a very important role in degradation of perovskite solar cells 55 – 59 , especially under high-humidity testing conditions. The next important features which affect stability are molecular weight and concentration of precursor solution.…”

Observing Defect Passivation of the Grain Boundary with 2‐Aminoterephthalic Acid for Efficient and Stable Perovskite Solar Cells

“…Fortunately, several recent studies have reported that additive engineering is an effective alternative strategy. Various additives, such as polymers, small molecules, and semiconductor molecules, have been incorporated into perovskite precursor solutions . Although additives containing N, O, and S atoms with lone pairs of electrons were found to be efficient in passivating defects in perovskite films and further enhanced charge transfer and collection, they lacked sufficient evidence to demonstrate that the defect passivation undoubtedly occurred at GBs .…”

“…The organic compound contained a benzene ring, an ammonium group (−NH 2 ), and two carboxyl groups (−COOH). The molecules could easily assemble at the GBs because the benzene ring had a high cohesive energy due to its robust structure and the strong interaction of its π–π bonds . Owing to the existence of a benzene ring, it was also facile to form a hydrophobic passivating layer that prevented the permeation of moisture along the GBs.…”

Effective Phase‐Alignment for 2D Halide Perovskites Incorporating Symmetric Diammonium Ion for Photovoltaics

“…The organic cations in 2D perovskites have been shown to keep water molecules away from the reaction site by straining the Pb-I bond on the surface. [48][49][50][51][52][53] In addition, the new structure incorporating diammonium ions is more conducive to charge transport because the distance between the inorganic layers is shorter and has more 3D-like characteristics in contrast to the (A) 2 A′ n-1 M n X 3n+1 2D perovskites. [20,[26][27][28][29][30]54] Although molecular-chemistry-dependent structure and optoelectronic properties of the AA′ n−1 M n X 3n+1 type 2D perovskites have been demonstrated, unfortunately, a series of low-n AA′ n−1 M n X 3n+1 perovskite devices reported currently shows poor performance.…”