Pressure-induced emission enhancement with an abnormal blue shift of the Sb3+-doped zero-dimensional lead-free halide perovskite Cs2InBr5·H2O

Zero-dimensional (0D) lead-free halide perovskites doped with ${\mathit{ns}}^{2}$-metal ions have emerged as an interesting research topic, due to their broad luminescence spectra and large Stokes shift for both fundamental research and future optoelectronic applications. Herein, we report an abnormal phenomenon of pressure-induced blue-shifted and enhanced emission in ${\mathrm{Sb}}^{3+}$-doped ${\mathrm{Cs}}_{2}{\mathrm{InBr}}_{5}\ifmmode\cdot\else\textperiodcentered\fi{}{\mathrm{H}}_{2}\mathrm{O}$. The pressure-induced photoluminescence enhancement (0.6 GPa) of ${\mathrm{Sb}}^{3+}$:${\mathrm{Cs}}_{2}{\mathrm{InBr}}_{5}\ifmmode\cdot\else\textperiodcentered\fi{}{\mathrm{H}}_{2}\mathrm{O}$ can be ascribed to the less energy difference between ${}^{3}{P}_{1}$ of ${\mathrm{Sb}}^{3+}$ and self-trapped exciton (STE) state, and the reduced nonradiative energy loss. Meanwhile, the pressure-induced anisotropic contraction of inhomogeneously coordinated [${\mathrm{SbBr}}_{5}\mathrm{O}]{\mathrm{H}}_{2}^{2\ensuremath{-}}$/[${\mathrm{InBr}}_{5}\mathrm{O}]{\mathrm{H}}_{2}^{2\ensuremath{-}}$ octahedra is highly responsible for the unusual blue-shifted STE emission and the variation of the band gap. These findings provide a basis for understanding the structure-properties correlation of ${\mathit{ns}}^{2}$-metal ions doped 0D perovskite, and shed light on the effects of the pressure in emission enhancement and tuning the optical properties of halide perovskites.