Differing vibrational properties of halide and chalcogenide perovskite semiconductors and impact on optoelectronic performance

We report a comparative study of temperature-dependent photoluminescence and structural dynamics of two perovskite semiconductors, the chalcogenide BaZrS3 and the halide CsPbBr3. These materials have similar crystal structures and direct band gaps, but we find that they have quite distinct optoelectronic and vibrational properties. Both materials exhibit thermally activated nonradiative recombination, but the nonradiative recombination rate in BaZrS3 is four orders of magnitude faster than in CsPbBr3, for the crystals studied here. Raman spectroscopy reveals that the effects of phonon anharmonicity are far more pronounced in CsPbBr3 than in BaZrS3. Further, although both materials feature a large dielectric response due to low-energy polar optical phonons, the phonons in CsPbBr3 are substantially lower in energy than in BaZrS3. Our results suggest that electron-phonon coupling in BaZrS3 is more effective at nonradiative recombination than in CsPbBr3 and that BaZrS3 may also have a substantially higher concentration of nonradiative recombination centers than CsPbBr3. The low defect concentration in CsPbBr3 may be related to the ease of lattice reconfiguration, typified by anharmonic bonding. It remains to be seen to what extent these differences are inherent to the chalcogenide and halide perovskites and to what extent they can be affected by materials processing.