Impact of Bi3+ and Cu2+ doping on the optical and electronic properties of CsPbBr3 for Photocatalytic toluene oxidation

Abstract

The doping of metal halide perovskites (MHP) offers the opportunity to introduce trap states that are reported to be beneficial for the charge carrier dynamics. Here, we investigated the electronic-structure-photocatalytic relationship of CsPbBr3 doped with Bi3+ and Cu2+ cations. Bi-doping necessitates a decrease of the hot injection temperature to avoid the formation of Bi nanoparticles, which leads to the formation of two-dimensional CsPbBr3 with a variable aspect ratio. The Bi doping causes no significant changes in the band gap energy but leads to a gradual appearance of band-tail in the absorbance and broad-band emission peak covering a large wavelength range. A photoluminescent quenching is observed as the ratio of Bi3+ increases, indicating shallow trap generation. Cu2+ doping does not affect the morphology of the 3D crystalline CsPbBr3 and shows a photoluminescent blueshift, which translates change in the band gap energy. The CsPbBr3 doping, with an adequate amount of Cu, provides the best photocatalytic activity, surpassing Bi-doped CsPbBr3. Time-resolved photoluminescence analysis indicated that Bi3+ introduced a shallow trap that captures electrons, leaving the holes free, leading to an increase in the charge carrier lifetime, thus favoring charge carrier separation. Unlike bismuth, Cu2+ affects both conduction and valence band positions, making the oxidation reaction more favorable.