Air-Processed All-Inorganic Halide Perovskites Integrated Photorechargeable Supercapacitors.

Abstract

Due to their easy integration for self-powered operation, integrated energy harvesting and storage could be the game changer in smart, flexible, and portable electronic devices. Three-electrode integration is the most promising approach among all possible configurations because it is less complex and compatible with most techniques. Although the photoconversion efficiency has increased above 20% due to the integration of high-performance perovskite solar cells, the electrochemical storage efficiency (efficacy of the integration) is much below 80% due to a significant potential drop and impedance mismatch. In this context, we introduced perovskite-based solid-state thin film supercapacitors integrated with stable, air-processed perovskite solar cells for an uninterrupted power supply. Our measurement shows that the best performance can be achieved by optimizing several parameters, including series-connected solar cells, light intensity, and photovoltaic active area. The critical challenge with these integrated systems is to maintain a uniform charging current of the supercapacitors throughout the charging cycle while minimizing self-discharging. We achieved an electrochemical storage efficiency of ∼87% at an overpotential of 0.8 V. The overpotential can be as low as 2 mV. We fabricated fully solution-processed series-connected solar cells to integrate with stacked supercapacitors to improve the operating voltage beyond 2.1 V. The photocharging and dark discharging of these integrated devices have been tested over 200 cycles, and a negligible drop in efficiency has been observed. Our detailed energy conversion and storage analysis in these systems unveils the mechanism and losses due to three-terminal integration.