Abstract
Doublet luminescence from hybrid metal trihalide perovskite semiconductors is observed along with materials processing when high-quality single crystals are obtainable. Yet, the underlying physical mechanism remains poorly understood. Here, we report controllable solution-processed crystallization that affords high-quality CH3NH3PbBr3 single crystals with atomically flat pristine surfaces. Front-face photoluminescence (PL) shows doublet luminescence components with variable relative intensities depending on the crystal surface conditions. We further find that the low-energy PL component with asymmetric spectral line-shape becomes predominant when the atomically flat crystal surfaces are passivated in the ion-abundant saturated solutions, while poor-quality single crystal with visually rough surface only gives the high-energy PL with symmetric line-shape. The asymmetric spectral line-shape of the low-energy PL matches perfectly with the simulated bandedge emission. Therefore, the low-energy PL component is attributable to the intrinsic bandedge emission from the crystal bulk while the high-energy one to surface-specific emission. Elliott fitting to the absorption data and multi-exponential fitting to the time-resolved photoluminescence traces jointly indicate the coexistence of excitons and electron–hole plasmas in optically excited CH3NH3PbBr3 single crystals, thereby catching the physical merit that leads to the occurrence of doublet luminescence.
Published Version
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