Trade-off between areal capacitance and optical transmittance of highly transparent MnO2 electrodes for supercapacitors

In this study, the capacitive performance of ultrathin-film manganese oxide (MnO2) electrodes for transparent supercapacitors is investigated. The highest transmittance reported so far, 99.1% at a 550 nm wavelength, is achieved with an areal capacitance of 1.6 mF/cm(2). The thickness and resulting optical transparency of the MnO2 films can easily be controlled by changing the concentration of the precursor sols in the sol-gel-derived coating process. The thinnest electrode shows the highest transmittance and specific capacitance of 576 F/g. The relationship between the transmittance, optical conductivity and areal capacitance of the electrodes is also investigated. The largest capacitive figure of merits, FoMc, of 62.7 cm(2)/F is obtained for the thinnest electrode. Deconvolution of the capacitive elements indicates that the surface capacitive element is dominant for the ultrathin electrodes, whereas the contribution of the diffusion-controlled insertion element grows rapidly as the electrode thickness increases.

Automated summary

The study investigates the capacitive performance of ultrathin-film manganese oxide electrodes for transparent supercapacitors. It is found that the thickness and optical transparency of the MnO2 films can be controlled by adjusting the concentration of the precursor sols. The thinnest electrode exhibits the highest transmittance and specific capacitance.