Lightweight Flexible Polyimide-Derived Laser-Induced Graphenes for High-Performance Thermal Management Applications

Laser pyrolysis of polyimide (PI) is a promising approach for preparing porous graphenes with hierarchical structures. In this study, we used a dual-focusing lens with a collimator to generate a highly concentrated CO2 laser beam with a high focal energy density. The resulting PI-derived graphene (PIDG) obtained under high-intensity laser irradiation possessed a high degree of graphitization, a low sheet resistance (27.4 Ω/sq.), and a large surface area (240.4 m2/g). Through optimization of the high-intensity laser parameters, we obtained a hierarchical PIDG possessing a fiber-like structure. We used this PIDG as a flexible heater and efficient heat sink for Si photovoltaic (PV) and light-emitting diode (LED) modules. The developed heater could reach a temperature of 202.6 °C under an applied voltage of 16 V, with rapid responses and remarkable flexibility. As a result of improved convective and radiative heat dissipation, the PIDG-based heat sink lowered the operating temperatures of the Si PV and LED modules efficiently. Accordingly, the power conversion efficiency of the Si PV and the lifetime of the LED module both increased dramatically.