2, Diamond Light Source, Didcot, , United Kingdom
In the last 6 years, hybrid halide perovskites have emerged as a highly efficient class of solar absorbers, with efficiencies reaching 22.4 %, quickly surpassing other 3rd generation devices. The highest performing hybrid perovskite is the cubic CH3NH3PbI3 (MAPI), which is made from earth-abundant elements and can be easily solution processed, dramatically reducing manufacturing costs. Unfortunately, chemical stability is a major concern for these materials and much effort has been devoted to increasing the stability of MAPI based devices.
Recently, partial substitution of iodine with the pseudohalide ion, SCN–, to form the layered (CH3NH3)2Pb(SCN)2I2 (MAPSI), has been suggested as novel route to increase stability whilst retaining high efficiencies. In this work, we explain why MAPSI can still possess an ideal electronic structure for light absorption, despite the loss in connectivity when moving from a cubic to a layered structure. We also explain, for the first time, why MAPSI is more stable than MAPI. Lastly, we demonstrate that MAPSI can act as a parent structure for a related family of materials whose optoelectronic properties can be fine-tuned for use in photovoltaic applications. We further screen this extended family for their defect properties and suggest solar cell architectures likely to result in efficient devices.
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