Effect of Dimensionality on the Optical Absorption Properties of CsPbI3 Perovskite Nanocrystals
Abstract
The band-gaps of CsPbI3 perovskite nanocrystals are measured by absorption spectroscopy at cryogenic temperatures. Anomalous band-gap shifts are observed in CsPbI3 nanocubes and nanoplatelets, which are modeled accurately by band-gap renormalization due to lattice vibrational modes. We find that decreasing dimensionality of the CsPbI3 lattice in nanoplatelets greatly reduces electron-phonon coupling, and dominant out-of-plane quantum confinement results in a homogeneously broadened absorption lineshape down to cryogenic temperatures. An absorption tail forms at low-temperatures in CsPbI3 nanocubes, which we attribute to shallow defect states positioned near the valence band-edge.
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