We investigated the fundamental properties of MAPbBr ₃ single crystal by applying temperature-dependent x-ray diffraction and photoluminescence (PL) measurements from 10 K to 270 K. The structural and spectral analyses illustrate the phase transitions of MAPbBr ₃ single crystal from cubic phase ( α -MAPbBr ₃ ) to tetragonal phases ( β -MAPbBr ₃ and γ -MAPbBr ₃ ), and then to orthorhombic phase ( δ -MAPbBr ₃ ) at ~230 K, ~160 K and ~150 K, respectively. The Time-resolved PL results show that both free excitons (FE) and bound excitons (BE) have contributions to the PL emissions. The PL at high temperature mainly originates from the BE transitions, while the PL at low temperature ( δ -MAPbBr ₃ phase) comes from both BE and FE transitions, and the FE related PL becomes more and more dominant at lower temperatures. The first-principle calculation at zero temperature reveals that the BE-related PL was caused by defects from the anti-site substitution of MA and Br ions.

We report the fabrication of large-area holographic diffraction gratings on a curved surface from transferred photopolymer films by introducing a water-soluble interlayer. The holographic gratings on a curved surface have a diffraction efficiency of $\sim 63\%$, which is $\sim 80\%$ of the recorded holographic film on a flat surface. By transferring a recorded holographic grating to a flat substrate, we obtained rainbow holographic gratings under white light illumination. This can be explained by the deformation of the holographic gratings. Our result provides a low-cost method for fabricating diffraction optical elements on a curved surface for optical systems.