Optoelectronic functionality and photovoltaic performance of Sr-doped tetragonal CH₃NH₃PbI₃: A first-principles study

The electronic, optical and transport properties, and photovoltaic performances of tetragonal CH₃NH₃PbI₃ with various Sr substitutions for Pb (3.12%, 6.25%, 12.5% and 25%) have been systematically investigated using the first principles method. It is discovered that the 25% Sr content not only reduces the band gap by over 10% to harvest the near-infrared phonons, but also substantially promotes the charge transport through lowering the carrier effective mass and enhancing the carrier mobility. Simultaneously, CH₃NH₃Pb_0·75Sr_0·25I₃ is conservatively estimated to have a power conversion efficiency of about 19%, showing the improved photovoltaic performance. Further, the phonon-dispersion and formation-energy calculations reveal that CH₃NH₃Pb_0·75Sr_0·25I₃ is of high dynamic and structural stabilities. The overall improvements in optoelectronics and photovoltaics make CH₃NH₃Pb_0·75Sr_0·25I₃ promising as an effective optical absorber of solar cells. In contrast, the influences of lower Sr contents are slight. This work provides a theoretical perspective in optimizing the optoelectronic and photovoltaic applications of CH₃NH₃PbI₃.