Understanding the Correlation Between Temperature Dependent Performance and Trap Distribution for Nickel Oxide Based Inverted Perovskite Solar Cells

The distribution of trap states in the active layer of perovskite solar cells is a key limiting factor that largely controls the charge carrier mobility, rate of recombination of trapped charges, and, subsequently, the power conversion efficiency. In the present study, the charge carrier dynamics and the influences of the energetic distribution of trap states over device performance of nickel oxide based inverted perovskite solar cells have been investigated in detail by analyzing their temperature dependent transient photoresponses. The reduction in temperature during electrical measurement has induced anomalous behavior in current-voltage characteristics and distribution of trap states. The tail states energy of the valance band decreases from 150 to 50 meV as the temperature of the transient photocurrent measurement increases from 83 to 300 K. The applied bias significantly influences the shape and location of the density of states distribution, indicating their ionic origin. The transient photovoltage measurement revealed that the devices show rapid recombination of localized photogenerated charge carriers around the orthorhombic to the tetragonal phase transition region. The detailed study of trap state analysis and their various impacts on the device performances will prove beneficial for the fundamental understanding of the device physics, material design, and performance stabilization for perovskite solar cells and related devices.