Laser-Patterned Nitrogen–Carbon Materials for Flexible, Quasi-Solid-State Supercapacitors

Abstract

Laser-induced carbonization is a versatile processing technique for the direct writing of porous carbon patterns onto polymer sheets. We further broaden its capabilities to pattern nitrogen–carbon (N–C) materials such as graphitic carbon nitride (g-CN), and report on a hybrid N–C/porous carbon material carefully designed for quasi-solid-state microsupercapacitor device applications. A multilayer precursor is prepared by screen-printing the product of an autoclave-assisted synthesis of urea and citric acid onto a flexible polyimide (PI) substrate. This assembly is carbonized using IR and UV lasers. The resulting hybrid patterns are composed of g-CN quantum dots, particles, and flakes as the top layer, and porous carbon as the bottom layer. The N-rich entities on top facilitate an electrochemically active functional material, while the bottom layer serves as the current collector. A seamless transition between the two layers, combined with a binder-free device construction, enables full utilization of the surface and properties of the N–C materials. The devices demonstrate an areal capacitance of 107.8 mF/cm² at 0.5 mA/cm² and an areal energy and power density of 9.86 uWh/cm² and 164 uW/cm², respectively. In addition to device fabrication and testing, we compare the carbonization mechanisms under UV and IR lasers, and propose an interdependent carbonization mechanism that supports secondary laser-carbonization of the underlying polymer.