Relationship between the molecular structure of polyimide and its dielectric properties: Optimizing performance for triboelectric nanogenerators

Triboelectric nanogenerators (TENGs) are eco-friendly energy harvesters. Polyimide (PI) has been widely used as a triboelectric layer in TENGs, but the relationship between its structure and performance is not fully understood. Herein, PI films with varying molecular structures were prepared to investigate the effects of -O- and –CF₃ groups on their physical properties and triboelectric performance. The results showed that PI films with -O- exhibited better thermal stability, while both -O- and –CF₃ groups effectively modulated optical transparency and dielectric properties. At 450 nm, M6-PI and O6-PI exhibited the highest transmittance at 63.14 % and 55.06 %, respectively, with dielectric loss performance below 0.5 % at 10⁵ Hz. PI films incorporating -O- and –CF₃ demonstrated significant improvements in triboelectric performance. Theoretical calculations clarified these groups influence optical transparency, dielectric properties, and electrical output performance. Ultimately, the fabricated 6PI-TENG achieved the desired triboelectric performance with enhanced electrical output. The V_oc and Q_sc of 6PI reached approximately 80 V and 25 nC, respectively. This study offers essential theoretical insights for designing and advancing of TENGs, contributing to sustainable energy development.