Understanding the Impact of Bismuth Heterovalent Doping on the Structural and Photophysical Properties of CH3 NH3 PbBr3 Halide Perovskite Crystals with Near-IR Photoluminescence.

A comprehensive study unveiling the impact of heterovalent doping with Bi3+ on the structural, semiconductive, and photoluminescent properties of a single crystal of lead halide perovskites (CH3 NH3 PbBr3 ) is presented. As indicated by single-crystal XRD, a perfect cubic structure in Bi3+ -doped CH3 NH3 PbBr3 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 Bi3+ dopants as nonradiative recombination centers, which explains the observed transition from bimolecular recombination in pristine CH3 NH3 PbBr3 to a dominant trap-assisted monomolecular recombination with Bi3+ doping. Electrically, it is found that the mobility in pristine perovskite crystals can be boosted with a low Bi3+ 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 (Ea ) for electrical conductivity. The reduction of Ea 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 Bi3+ concentration shed light on the opportunity to apply heterovalent doping of perovskite single crystals for NIR optoelectronic applications.