Unusual luminescence and its decay behavior of CH3NH3PbBr3 single crystals at orthorhombic phase

We investigate the luminescent property of CH 3 NH 3 PbBr 3 (MAPbBr 3 ) single crystals (SCs) by use of temperature and power dependent photoluminescence (PL) spectroscopy. An unusual PL due to trapped state emission at 580∼650 nm can be only observed at orthorhombic phase below 145 K, which is originated from the change of structural order and disorder at low temperature. At the temperature point from orthorhombic to tetragonal phase, the structural change leads to the disappearance of trapped state emission. From Raman spectra and theoretical analysis, MAPbBr 3 crystal structure is susceptible to temperature, trapped state emission can be formed after photoinduced excitation due to the tilting and twisting of MA organic group, which even exist under near-infrared (NIR) femtosecond laser excitation due to two-photon absorption. Time-resolved PL (TRPL) reveals that temperature-dependent characteristics of this unusual PL coexist with intrinsic exciton recombination at orthorhombic phase. Our findings imply that it is essential to understand the photophysical property caused by the structural change of hybrid perovskite crystal. • Unusual photoluminescence characteristics of MAPbBr 3 single crystal are studied at orthorhombic phase. • Theoretical simulations and Raman experiment further prove the tilting and twisting of structure on the optical properties. • A defect energy level model is proposed to explain the unusual luminescence behavior.