Unveiling the Mechanism of Induced Charge Transport in Droplet-Based Triboelectric Nanogenerator

The droplet-based triboelectric nanogenerator (D-TENG) represents a promising paradigm for droplet energy harvesting. However, D-TENG still faces serious problems, such as the high equivalent impedance and the voltage curve that deviates from the theory, which will lead to a low energy utilization efficiency. The well-accepted mechanism generally neglects the effect of the solid-liquid interface on charge transport rate, remaining it incompletely understood at the solid-liquid interface. Notably, this knowledge gap manifests in the systematic discrepancy between theoretical predictions and experimental measurements, as well as the equivalent impedance. Here, a series of D-TENG devices with different intrinsic capacitance are constructed and measured and the transport process of induced charges is analyzed at the electrical double layer (EDL) of droplet/top electrode interface. It is demonstrated that the space charge effect limits the rate of induced charge transfer, and the intrinsic capacitance of D-TENG can affect the strength of this limitation. The factors that affect equivalent impedance are clarified in the experiments: intrinsic capacitance of D-TENG and droplet concentration. A maximum charge density and a low equivalent impedance are achieved ≈4.25 mC m^-2 and 5000 𝛀, respectively. These findings propose a new induced charge transfer mechanism and a novel approach for reducing equivalent impedance. © 2025 Wiley-VCH GmbH.