Phase Segregation in Cs-, Rb- and K-Doped Mixed-Cation (MA)(x)(FA)(1-x)Pbl(3) Hybrid Perovskites from Solid-State NMR

Hybrid (organic-inorganic) multication lead halide perovskites hold promise for a new generation of easily processable solar cells. Best performing compositions to date are multiple-cation solid alloys of formamidinium (FA), methylammonium (MA), cesium, and rubidium lead halides which provide power conversion efficiencies up to around 22%. Here, we elucidate the atomic-level nature of Cs and Rb incorporation into the perovskite lattice of FA-based materials. We use Cs-23, Rb-87, K-89, C-13, and N-14 solid-state MAS NMR to probe microscopic composition of Cs-, Rb-, K-, MA-, and FA-containing phases in double-, triple-, and quadruple-cation lead halides in bulk and in a thin film. Contrary to previous reports, we have found no proof of Rb or K incorporation into the 3D perovskite lattice in these systems. We also show that the structure of bulk mechanochemical perovskites bears close resemblance to that of thin films, making them a good benchmark for structural studies. These findings provide fundamental understanding of previously reported excellent photovoltaic parameters in these systems and their superior stability.

Published in:
Journal Of The American Chemical Society, 139, 40, 14173-14180
Washington, American Chemical Society

 Record created 2017-11-08, last modified 2018-12-03

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