Synthesis and applications of NPB derivatives as hole transport molecules for performance manipulation of fiber-based triboelectric nanogenerators

Nanofibers are emerging as a crucial component in triboelectric nanogenerators (TENGs) to enhance energy extraction from dissipated mechanical work. Polymer fiber-based triboelectric nanogenerators (PF-TENGs) are particularly prominent due to their numerous advantages, such as facile synthesis, affordability, eco-friendly production, and the ability to integrate into a wide range of applications. However, due to the surface charge mitigation mechanism, its complex material network suffers from insufficient charge production. Thus, chemical modification of triboelectric polymer matrix through molecular design and processing of modified structures via materials engineering is a feasible mechanism to promote surface charge. Herein, we showed the synthesis and application of three novel NPB-based hole transport organic molecules to enhance charge production and improve the fabricated device output. Modifying the main molecular body with distinct side groups enabled us to play with the resonance and inductive effects of the molecules. This modification resulted in the ability to tune the HOMO levels of the molecules. The application of these molecules also gave rise to both structural and topological alterations of the nanofibers that changed the surface features of the fiber films. As for TENG parameters, this strategy produced, in turn, 52% and 74% enhancement in instant voltage and power values compared to the reference device under the same experimental conditions. Under external electrical loads, the increase in the voltage reached 50%, and the recorded maximum value was 598 V. In contrast, the highest current value of 52.5 µA corresponds to a 67% enhancement compared to the reference TENG. The outcome of this study provides a significant improvement of the materials processing methodology, which applies to future printable and flexible TENG devices and further contributes to material design for improved tribotronic systems using the integration of dielectrics and semiconductors.