Overcoming the Trade‐Off between Optical Transmittance and Areal Capacitance of Transparent Supercapacitors for Practical Application

Abstract

It is substantially challenging for transition metal oxide nanoparticle (NP)-based electrodes for supercapacitors to achieve high transparency and large capacity simultaneously due to the inherent trade-off between optical transmittance (T) and areal capacitance (C_A ). This study demonstrates how this trade-off limitation can be overcome by replacing some electrode NPs with transparent tin oxide (SnO₂ ) NPs. Although SnO₂ NPs are non-capacitive, they provide effective paths for charge transport, which simultaneously increase the C_A and T_550nm of the manganese oxide (Mn₃ O₄ ) NP electrode from 11.7 to 13.4 mF cm^-2 and 82.1% to 87.4%, respectively, when 25 wt% of Mn₃ O₄ are replaced by SnO₂ . The obtained C_A values at a given T are higher than those of the transparent electrodes previously reported. An energy storage window fabricated using the mixed-NP electrodes exhibits the highest energy density among transparent supercapacitors previously reported. The improved energy density enables the window to operate various electronic devices for a considerable amount of time, demonstrating its applicability in constructing a reliable and space-efficient building-integrated power supply system.