Weak Temperature-Dependent Hole Injection and Electron-Hole Recombination at CH3NH3PbI3/NiO Heterojunction: A Time-Domain Ab Initio Study
Inorganic hole transport material (HTM) NiO is superior to the traditional organic HTMs due to the high stability and conductivity. Efficient charge separation and slow charge recombination are two key important steps in determining the efficiency of solar cells but they often show strong temperature dependence. Using nonadiabatic molecular dynamics combined with ab initio time-domain density functional theory, we have demonstrated that the time scales for both hole transfer and electron-hole recombination show weak temperature-dependent in MAPbI3/NiO perovskite solar cells. The hole transfer occurs on sub-100fs at both and high and low temperature. Hole transfer proceeds slightly faster at high temperature than low temperature due to enhanced NA coupling. Notably, the over 200 fs energy relaxation remains the hole hot before cooling to interacting with the remaining electron and forming exciton and accelerating electron-hole recombination, providing an excellent advantage for solar energy applications. Following charge separation, the electron-hole recombination takes place on several nanoseconds at both low and high temperature. The acceleration is only by a factor of below 2 arises due to that increased atomic motions cause rapid loss of coherence, which competes successfully with the enhanced NA coupling. The detailed atomistic understanding of the reported results allows us to generalize the conclusions to other hole transport materials, and suggest weak temperature-dependent charge dynamics properties enabling high performance of perovskite solar cells.
- This article is part of the themed collection: 2019 Journal of Materials Chemistry A HOT Papers