Effect of Interfacial Ionic Defects in Perovskite Solar Cells and their Mitigation Mechanism: A Comprehensive Theoretical Analysis with Experimental Validation

Interfacial ionic defects in perovskite solar cells (PSCs) significantly influence the efficiency and long-term stability. In this study, primarily simulation-assisted analyses are conducted to explore the capacitive effect of these defects on the performance of PSCs through impedance analysis. Simulated data indicate a decrease in capacitance with increasing frequency, leading to a higher built-in potential (Delta Vbi = 150 mV). Moreover, an increase in capacitance with increasing light intensity is observed. Additionally, reducing the ionic defect concentration at the interfaces (from 1019 to 1016 cm-3) results in more significant band bending and a higher Vbi. Potential solutions to mitigate interfacial ionic defects, including doping at transport layer interfaces are proposed. Doping at both interfaces introduces an energy spike (valence band offset) of 0.21 eV and a cliff (conduction band offset) of 0.16 eV, respectively, for holes and electrons, leading to an improvement in the open circuit voltage (VOC). Finally, experimental results demonstrate a notable enhancement in VOC of 0.04 V with the introduction of Li+ doping at the electron transport layer/perovskite interface. These findings provide essential perceptions for effectively mitigating the effect of interfacial ionic defects on the performance of PSCs and enhance their overall performance. This simulation analysis offers valuable insights into understanding capacitance modulation by interfacial defects under varying applied potential and light intensity conditions. Additionally, we proposed potential solutions to mitigate interfacial ionic effects, notably through doping at transport layer interfaces. This approach introduces energy spikes and cliffs for holes and electrons, respectively, leading to enhancements in the open circuit voltage (VOC). image