Large-area (64 cm²), semi-transparent, flexible all-solid-state supercapacitor using D-bar coating process

In this work, we report large-area, semi-transparent, and flexible all-solid-state supercapacitors (ASSCs) fabricated using scalable D-bar coating, which is compatible with roll-to-roll printing processes. The poly (3,4-ethylenedioxythiophene):poly (styrene sulfonate) (PEDOT:PSS)-based transparent conducting electrodes (TCEs) show optical transparencies of T_550nm > 85% and conductivities of ~3645 S cm⁻¹. An ASSC device (~1 cm²) consists of D-bar coated TCEs and PVA/LiCl gel-electrolyte and exhibits a high areal capacitance per electrode (C_a) of 4.7 mF cm⁻², which is about 35% higher than that of ASSC devices containing spin coated TCEs. A PEDOT:PSS ASSCs with the transparency of T_550nm > 65% presents stable capacitance up to 10,000 charge/discharge cycles and 5000 bending cycles at a bending radius of 2 mm, demonstrating excellent electrochemical robustness and flexibility. Moreover, the large-area (~64 cm²) ASSC fabricated with D-bar coating exhibited a C_a of 2.9 mF cm⁻², a maximum energy density of 18 µWh cm⁻² and a power density of 1600 µW cm⁻², which outperforms state-of-the-art transparent and flexible ASSCs. The agglomerated PEDOT:PSS nanofibrils and dipper pore size on D-bar coated TCEs, enables efficient ion adsorption/desorption and charge intercalation, which leads to the high performance of the flexible ASSC.