Effects of surface morphology on the ionic capacitance and performance of perovskite solar cells

The accumulated ionic interface charge (IIC) affects the performance of perovskite solar cells significantly. In this study, we establish a model to describe the formation of capacitance. Mobile ions in perovskite accumulate at the interface and form a plate capacitor with screen charge on the electrodes. Reducing the roughness of perovskite or covering with a thick electron transporting layer significantly regulates the ionic capacitance. The results indicate that mobile ions exist in the perovskite layer, the accumulated IIC density is determined by the thickness of the carrier transport layer, and the capacitor area is affected by interface roughness.