Scalable, All-Printed Photocapacitor Fibers and Modules based on Metal-Embedded Flexible Transparent Conductive Electrodes for Self-Charging Wearable Applications

The popularity of wearable smart electronic gadgets, such as smartphones, smartwatches, and medical sensors, is inhibited by their limited operation lifetime due to the lack of a sustainable self-charging power supply. This constraint can be overcome by developing a flexible, self-charging photocapacitor that can synchronously harvest and store energy. Here, ultrathin, all-printed, and metal-embedded transparent conducting electrodes (ME-TCEs) are designed for the fabrication of large-area, flexible organic solar cells (F-OSCs) and flexible supercapacitors (F-SCs). Stripe-shaped F-OSCs (SF-OSCs) and F-SCs (SF-SCs) are obtained via slitting the as-fabricated F-OSCs and F-SCs with a surgical scalpel, respectively. The SF-OSCs and SF-SCs fully retain their performance after slitting, achieving a power conversion efficiency of ≈6.43% and areal capacitance of ≈52 mF cm⁻², respectively. Furthermore, photocapacitor fibers are obtained by vertically stacking one SF-OSC and seven SF-SCs. Each fiber is fully encapsulated using UV-curable resin. When woven into a textile, the photocapacitor module (2 series × 4 parallel connections) is able to charge up to a voltage of 3.2 V in 5 min under one-sun illumination. The photoelectric-conversion-and-storage efficiency (η) of the photocapacitor module is 4.94%. The highly tailorable, mechanically robust photocapacitor demonstrated herein can be a secondary, self-sustainable power supply for futuristic wearable applications.