Insight into efficient photoluminescence regulation mechanism by lattice distortion and Mn doping in organic-inorganic hybrid perovskites.

The space configurations of organic ammonium cations play a vital role in indirectly revealing the relationship between the structures and photoluminescence properties. Structural transformation induced tunability of the photophysical properties has rarely been reported. In this work, two organic-inorganic halide perovskites with different octahedral distortions were synthesized to explore the relationships between "steric effect" of organic cations and photoluminescence properties. The broadband emission of (DETA)PbBr·HO with high octahedral distortion is attributed to self-trapped excitons and trap states, whereas smaller steric hindrance ammonium cation 1,4-butanediamine form a 2D layered perovskite with narrowband emission due to free excitons. More importantly, the photoactive metal ions Mn doping strategy gives rise to tunable broadband light emission from weak to strong orange emission with higher PLQY up to 20.96 % and 12.90% in 0D (DETA)PbMnBr·HO and 2D (BDA)PbMnBr respectively. Combined with time-correlated single photon counting and photoluminescence spectra, Mn-doped perovskites reveal energy transfer from host to Mn characteristic energy level (T-A). Importantly, defect states are reduced by doping manganese ions in (DETA)PbBr·HO to enhance photoluminescence intensity. This work sheds light on the mechanism of defect-related emission and provides a successful strategy for designing novel and adjustable materials.