Patterning Islandlike MnO2 Arrays by Breath-Figure Templates for Flexible Transparent Supercapacitors

Although plenty of active materials could be used as supercapacitor electrodes, only limited ones have been engineered to construct transparent supercapacitors. Specially, it is a great challenge to make opaque metal oxides, which often own high energy density, into transparent films. Here, we demonstrate a novel approach to fabricate transparent MnO2 films for flexible transparent supercapacitors. By utilizing breath-figure polymer films with ordered pores as template, arrays of MnO2 islands were electrochemically deposited, with high light transmission. The thickness and interspace distance of MnO2 island arrays could be adjusted by tuning deposition time so that the capacitance and transparency of the electrodes are changed accordingly. Such island array structure can effectively eliminate the internal stress existing in operation. The assembled transparent supercapacitor shows a transmittance of 44% at 550 nm and can yield a high capacitance of 4.73 mF/cm(2) at a current density of 50 mu A/cm(2), demonstrating high flexibility and stability.