Understanding the Impact of Bismuth Heterovalent Doping on the Structural and Photophysical Properties of CH NH PbBr Halide Perovskite Crystals with Near-IR Photoluminescence.

A comprehensive study unveiling the impact of heterovalent doping with Bi on the structural, semiconductive, and photoluminescent properties of a single crystal of lead halide perovskites (CH NH PbBr ) is presented. As indicated by single-crystal XRD, a perfect cubic structure in Bi -doped CH NH PbBr crystals is maintained in association with a slight lattice contraction. Time-resolved and power-dependent photoluminescence (PL) spectroscopy illustrates a progressively quenched PL of visible emission, alongside the appearance of a new PL signal in the near-infrared (NIR) regime, which is likely to be due to energy transfer to the Bi sites. These optical characteristics indicate the role of Bi dopants as nonradiative recombination centers, which explains the observed transition from bimolecular recombination in pristine CH NH PbBr to a dominant trap-assisted monomolecular recombination with Bi doping. Electrically, it is found that the mobility in pristine perovskite crystals can be boosted with a low Bi concentration, which may be related to a trap-filling mechanism. Aided by temperature (T)-dependent measurements, two temperature regimes are observed in association with different activation energies (E ) for electrical conductivity. The reduction of E at lower T may be ascribed to suppression of ionic conduction induced by doping. The modified electrical properties and NIR emission with the control of Bi concentration shed light on the opportunity to apply heterovalent doping of perovskite single crystals for NIR optoelectronic applications.