Efficient luminescent solar cells based on tailored mixed cation perovskites
Researchers developed a perovskite solar cell with high power conversion efficiency >20% and intense electroluminescence yield (0.5% We report on a new metal halide perovskite photovoltaic cell that exhibits both very high solar to electric power conversion efficiency and intense electroluminescence. We produce the perovskite films in a single step from a solution containing a mixture of FAI, PbI2, MABr, and PbBr2 (where FA stands for formamidinium cations and MA stands for methylammonium cations) Using mesoporous TiO2 and Spiro OMeTAD as electron and hole specific contacts, respectively, we fabricate perovskite solar cells that achieve a maximum power conversion efficiency of 20.8% for a PbI2/FAI molar ratio of 1.05 in the precursor solution. Rietveld analysis of x ray diffraction data reveals that the excess PbI2 content incorporated into such a film is about 3 weight percent. Time resolved photoluminescence decay measurements show that the small excess of PbI2 suppresses nonradiative charge carrier recombination. This in turn augments the external electroluminescence quantum efficiency to values of about 0.5% a record for perovskite photovoltaics approaching that of the best silicon solar cells. Correspondingly, the open circuit photovoltage reaches 1.18 V under AM 1.5 sunlight.
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