High-quality inorganic–organic perovskite CH₃NH₃PbI₃ single crystals for photo-detector applications

Single crystals of organolead trihalide perovskites (CH₃NH₃PbI₃) are supposed to be one of the most promising materials as photo-detectors. Because of their large absorption coefficient, long-range balanced electron, and hole-transport lengths, it is considered to break through the responsivity and efficiency. To systematically investigate the potentiality as photo-detector, high-quality CH₃NH₃PbI₃ single crystals with large size are highly demanded. In the paper, large CH₃NH₃PbI₃ single crystals with various crystal shapes were grown from γ-butyrolactone. At optimized precursor concentration and growth temperature, the growth rate was fixed at about 0.2 mm h⁻¹. Under such growth conditions, the growth steps, originated from screw dislocation on (100) facet, were revealed to be about 0.45 nm. This value is corresponded to half of the unit cell, implying the slow growth rate of (100) facet. With slow growth rate, the absorption edge of the CH₃NH₃PbI₃ single crystal was extended to 860 nm, correlated with a calculated bandgap of ~1.44 eV. By depositing a pair of Au electrodes, a metal–semiconductor–metal (MSM) photo-detector on the basis of the CH₃NH₃PbI₃ single crystal active layer (3 mm) was fabricated and its photo-response features were investigated systematically. About 2.531 A W⁻¹ responsivity was obtained from the device under 780 nm laser illumination, while the external quantum efficiency reached to 396.20 %, better than some GaN, GaAs, and GaP photo-detectors with a MSM device structure.