2, Sungkyunkwan University, Suwon-si, , Korea (the Republic of)
3, Sungkyunkwan University, Suwon-si, , Korea (the Republic of)
All-inorganic halide perovskite have received an enormous amount of attention because of unique properties, including facile deposition processing due to high solubility in polar organic solvents and tunability of band gap energy through manipulation of the halide composition, which is useful in solution-based fabrication of photonic and optoelectronic thin-film devices. To understand the intrinsic optoelectrical properties of inorganic perovskite, it is necessary to obtain high-quality inorganic perovskite samples, with a single phase, high purity, and a macroscopic size, known as crystals. Pure CsPbBr3 and Cs4PbBr6 single crystals were separately grown by AVC (anti-solvent vapor-assisted crystallization process) with dimensions of millimeters. We found the correlation between photocurrent generation and PL (photoluminescence) in perovskite crystals. The CsPbBr3 crystals, which have 3D perovskite structure, showed a sensitive steady-state photoresponse and a poor PL signal. Contrastively, the Cs4PbBr6 crystals, which have 0D perovskite structure, exhibited more than 1 order magnitude higher PL intensity than CsPbBr3, which generated an ultralow photocurrent under illumination. Photocurrent and PL have a negative relationship, which is ascribed to the recombination or dissociative process of excitons due to the difference of exciton binding energy. We attribute their contrasting opto-electrical characteristics to a difference of exciton binding energy, induced by coordination geometry of [PbBr6]4- octahedron sublattice. Our works indicate the importance of the crystal structure of perovskite materials in understanding their superior optoelectrical performance.