Effects of impurities on the cooling of photoexcited carriers in La1-xSrxCoO3-δ: A DFT and nonadiabatic molecular dynamics study

Photo-carrier relaxation in semiconductors determines their photon-conversion efficiency. Impurities have been proven to play an essential role in improving the efficiency and stability of perovskites. We studied the effects of Sr-doping and O-vacancies on the electronic band structure and photoexcited carrier cooling of perovskite-type LaCoO3 using density functional theory and nonadiabatic molecular dynamics methods. We found that the substitution of Sr2+ for La3+ in LaCoO3 leads to a semiconductor-metal transition, while a stoichiometric oxygen vacancy restores semiconductor properties in La1-xSrxCoO3-delta (delta = x/6). In addition, the oxygen vacancy basically changes the electronic band structures, and for visible light with low oxygen vacancy intensity, the photo-electron cooling can be reduced fourfold relative to that of pure LaCoO3. We clarify the functions of impurities, Sr-dopants, and O-vacancies in LaCoO3 and find that the average coupling strength between carriers (electrons/holes) and phonons can be used as a descriptor to characterize carrier relaxation, which is of great value for the further development of practical photo-conversion based on perovskites.

Automated summary

Photo-carrier relaxation is important for the efficiency of semiconductor photon-conversion, and impurities can improve the efficiency and stability of perovskites. Through theoretical calculations and simulations, we explored the effects of Sr-doping and O-vacancies on the electronic band structure and photoexcited carrier cooling in LaCoO3. We found that Sr-doping induces a semiconductor-metal transition, while O-vacancies restore semiconductor properties. Additionally, O-vacancies significantly affect the electronic band structure, leading to reduced photo-electron cooling. Our findings provide insight into the functions of impurities in perovskites and can contribute to the development of practical photo-conversion technologies.