Impact of Chemical Doping on Optical Responses in Bismuth-Doped CH₃NH₃PbBr₃ Single Crystals: Carrier Lifetime and Photon Recycling

Abstract

We studied the optical responses of organic-inorganic halide perovskite CH₃NH₃PbBr₃ single crystals doped with heterovalent Bi³⁺ ions (electron densities up to 2.3 × 10¹² cm^-3). The Bi doping causes no significant changes in the band gap energy but leads to an enhanced Urbach tail and photoluminescence blue shift. On the basis of the time-resolved photoluminescence measurements, we attribute the PL response to a shorter carrier lifetime induced by Bi doping, which results in a reduced photon recycling effect (i.e., the repeated emission and reabsorption of photons inside the crystal). We discuss the physical relation between Bi concentration and the optical and electric properties of Bi-doped CH₃NH₃PbBr₃ and reveal the unique nature of the Bi³⁺ ion as a dopant in halide perovskites.