Defect states of organic lead halide single crystals grown by inverse-temperature crystallization

We investigated the defect states of organic lead halide (CH3NH3PbX3: CH3NH3+) methylammonium (MA; X = Br- and I-) by using optical pulse-induced conductance transient spectroscopy. Organic lead halide single crystals having a bandgap ranging from 2.16 to 1.45 eV were grown by inverse temperature crystallization. The shallow trap energy level of MAPbBr(2.5)I(0.5) was E-v + 0.06 eV. The deep level traps of MAPbBr(3) and MAPbI(3) were E-v + 1.24 and E-v + 0.84 eV, respectively. The deep level traps of organic lead halide may have decreased the reactivity between iodide and bromide ions in the crystal lattice. Varying the ratio of halides in the perovskite can change the defect species in the crystals and can increase the photoconversion efficiency by decreasing the density of deep level traps.