IMF2017

Organometallic halide based perovskite solar cells (PSC) have shown exponential growth in energy conversion efficiency over the past couple of years making it one of the breakthrough materials of this decade. However there are some serious issues like toxicity of lead, poor durability in hot and humid conditions which are needed to be addressed before it can be used commercially. In the current investigation we synthesized environmentally benign lead-free novel bismuth based photo absorbers with double perovskite (A₂B₂I₆) as well as single perovskite (ABI₃) crystal structure having methylammonium and formamidinium in the A-site. The thin films perovskites were synthesized by solution chemistry and spin coating technique followed by annealing at optimized temperature. Transient photoluminescence (trPL) measurement exhibits high recombination time in these materials. Micrometer range large single crystals with hexagonal morphology were found in FESEM and fluorescence image analysis. Incorporation of Bi in the B-site of these perovskites provided superior moisture and temperature stability without compromising the high recombination time of lead based perovskites. The large single crystal formation was attributed to anti-solvent treatment in the thin-film processing. UV-Vis spectroscopy measurement demonstrated very high absorption coefficient in the visible spectrum and low optical band gap around 1.7 eV were obtained. Furthermore, ferroelectric properties of these materials were investigated by P-E loop measurement. The C-N, N-H bonds have been analyzed from FTIR spectra. TGA-DSC measurement of these samples confirmed good temperature stability.