TiO2/Cu2O heterojunction embedded PDMS composite with superhydrophobic surface for efficient raindrop energy harvesting

Abstract

Droplet-based triboelectric nanogenerators (TENGs) offer significant potential for environmental energy harvesting but are constrained by relatively low output performance. To overcome this bottleneck, this study proposes an interface engineering strategy integrating dielectric enhancement with built-in electric field regulation. n-Type titanium dioxide (TiO₂) and p-type cuprous oxide (Cu₂O) are co-incorporated into a polydimethylsiloxane matrix. This facilitates the in situ formation of p–n heterojunctions within the polymer network, yielding a TiO₂/Cu₂O heterojunction composite TENG (HC-TENG). The composite leverages multiple synergistic mechanisms. The high dielectric constant of TiO₂ enhances the polarization intensity of the triboelectric layer, inducing higher interfacial charge density. Simultaneously, the built-in electric field from the p–n heterojunction drives directional carrier separation, effectively suppressing charge recombination and dissipation. Furthermore, surface fluorination modification enhances charge trapping capabilities due to the high electronegativity of fluorine atoms, while the resulting superhydrophobicity acts as a physical barrier that prevents charge dissipation, thereby effectively stabilizing charge storage. Experimental results demonstrate that the optimized HC-TENG achieves significantly improved performance, with a peak output power of 3.4 mW. In practical demonstrations, a single droplet impact lights 400 commercial LEDs, and the device successfully powers a temperature and humidity sensor via a storage capacitor. This work elucidates the synergy among dielectric enhancement, built-in electric fields, and surface modification, providing a solid foundation for designing high-performance droplet energy harvesters.