High‐Efficiency Monolithic Photosupercapacitors: Smart Integration of a Perovskite Solar Cell with a Mesoporous Carbon Double‐Layer Capacitor

The integration of solar cells with supercapacitors into hybrid monolithic power packs can provide energy autonomy to smart electronic devices of the Internet of Things (IoT) by mediating between intermittent load and supply. Herein, such a photorechargeable supercapacitor (also called a photosupercapacitor) is developed via a three‐electrode integration of a p–i–n halide perovskite solar cell with a gel electrolyte‐type supercapacitor that uses mesoporous N‐doped carbon nanospheres (MPNC) as the active electrode material. Benefiting from the large surface area, well‐defined mesoporous structure, and homogeneous particle size of the MPNC material, the supercapacitor demonstrates high capacitance, resulting in large energy and power densities with a high charge/discharge efficiency. Its integration with a large‐area (1 cm 2 ) FA 0.75 Cs 0.25 Pb(I 0.8 Br 0.2 ) 3 perovskite solar cell, with an optimized layer sequence to minimize degradation, results in a photosupercapacitor exhibiting fast (< 5 s) photocharging up to 1 V. The outstanding peak overall photoelectrochemical energy conversion efficiency of 11.5% is a result of a high solar cell power conversion efficiency of 12.5%, a high supercapacitor storage efficiency of 92%, and low internal energy losses due to monolithic integration. These results underline the high potential of this type of device toward application in the IoT.