Observation of photoreflectance spectra of MAPbBr3 single crystal

초록

We reportthe firstobservationofphotoreflectance(PR)spectrainMAPbBr3 singlecrystalsandsystematicallyinvestigatetheir optical properties using photoluminescence (PL) and PR spectroscopies. High-quality MAPbBr3 single crystals were grown by the seed-induced inverse temperature crystallization method. Low-temperature PL measurements reveal four emission peaks at 2.09, 2.14, 2.17, and 2.20 eV. The 2.20 eV emission is attributed to free-exciton (FE) recombination, while the 2.14 and 2.17 eV peaks originate from bound-exciton (BE) recombination. The lowest-energy emission at 2.09 eV is associated with defect-related states in the orthorhombic phase. With increasing temperature, all PL emissions exhibit a blueshift, which is attributed to a thermally induced structural phase transition from the orthorhombic to the tetragonal phase occurring near 140 K. Consistent with the PL results, low-temperature PR measurements show a transition at 2.20 eV, corresponding to the FE-relatedband-to-bandtransition.ThePRtransitionenergyexhibitsablueshiftwithincreasingtemperaturefrom24to140K, followed by a redshift between 140 and 180 K, reflecting the orthorhombic-to-tetragonal phase transition. Electron–phonon interactions primarily govern the temperature-dependent energy shifts observed in both PL and PR spectra. Notably, the transition energies obtained from PR are higher than those from PL, which is attributed to the surface-sensitive band-to-band transitions probed by PR. The excellent agreement between PLandPRresultsconfirmsthereliability of the PR measurements and provides a comprehensive understanding of the excitonic and band-edge properties of MAPbBr3 single crystals.

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