Biexciton binding energy in CH3NH3PbBr3 as determined by multiphoton photoluminescence excitation spectroscopy

초록

High-quality halide perovskite single crystals ensure the existence of stable biexcitons, which are important for investigating many-body exciton physics and biexciton-based device applications. Recently, the biexciton binding energy (phi XX) in CH3NH3PbBr3 (MAPbBr3) single crystals was reported as-3.9 meV as deter-mined from the spectral distance between the exciton peak and the high-energy onset of the biexciton peak based on photoluminescence (PL) spectroscopy. However, the exciton PL peak is usually red-shifted compared with the true exciton level that is typically determined by the absorption measurement. Consequently, phi XX was significantly underestimated in the recent work. Here, we precisely locate the biexciton level by utilizing giant two-photon excitation specific to the biexciton resonance. We also independently estimate the true exciton level based on the steeply varying power exponent of the exciton PL by tuning the input wavelength for multiphoton excitation. As a result, the actual exciton level is determined to be-2251 meV at 10 K, thereby yielding a newly estimated phi XX = 10.2 (+/- 1) meV. This phi XX value is larger than a theoretical prediction based on variational calculations, which can be presumably attributed to polarization of the ionic components in MAPbBr3.

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