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

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 (CA ). 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 CA and T550nm 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 CA 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.

Effective Control of Chlorine Contents in MAPbI3- xCl x Perovskite Solar Cells Using a Single-Source Vapor Deposition and Anion-Exchange Technique.

In this study, a new method is developed to control the Cl-to-I ratio in MAPbI3- xCl x perovskite solar cells (PSCs) more easily and precisely using single-source vapor deposition of MAPbCl3 thin films and a subsequent anion exchange by repeated spin-coatings of methylammonium iodide (MAI) solution. This method can overcome the problems of previous vapor-deposition techniques for PSCs such as the occurrence of morphological defects in the films and difficulty in controlling the stoichiometry of the elements. The repetitive MAI treatments gradually fill the interstitial voids in the perovskite film and increase the average grain size up to 1.2 µm, which improves the charge-transfer property of the cells. The atomic Cl content, i.e., the x value, of the MAPbI3- xCl x film can also be simply controlled by changing the number of MAI treatments. The energy levels and resistive elements of the cells are strongly dependent on the x value of the MAPbI3- xCl x film. A maximum power conversion efficiency of 19.1% is achieved at x = 0.005.