Controlling Thermoelectric Properties of Laser-Induced Graphene on Polyimide.

In the field of wearable thermoelectric generators, graphene-based materials have attracted attention as suitable candidates due to their low material costs and tunable electronic properties. However, their high thermal conductivity poses significant challenges. Low thermal conductivity due to porous structure of the laser-induced graphene, combined with its affordability and scalability, positions it as a promising candidate for thermoelectric applications. In this study, thermoelectric properties of the laser-induced graphene (LIG) on polyimide and their dependence on structural modifications of LIG were investigated. Furthermore, it was shown that increasing the laser scribing power on polyimide results in larger graphene flakes and a higher degree of graphitization. Electrical conductivity measurements indicated an increase with increasing laser power, due to a higher degree of graphitization, which enhances charge carrier mobility. Our findings reveal that LIG exhibits p-type semiconducting behavior, characterized by a positive Seebeck coefficient. It was shown that increasing laser power increased the Seebeck coefficient and electrical conductivity simultaneously, which is attributed to a charge carrier energy filtering effect arising from structures occurred on the graphene flakes. Moreover, the porous structure of LIG contributes to its relatively low thermal conductivity, ranging between 0.6 W/m·K and 0.85 W/m·K, which enhances the thermoelectric performance of LIG. It has been observed that with increasing laser power, the figure of merit for laser-induced graphene can be enhanced by nearly 10 times, which holds promising applications for laser-induced graphene due to the tunability of its thermoelectric performance by changing laser parameters.