Super‐High Output Voltage Achieved in Droplet TENG by Substrate Dielectric Property Modulation

ABSTRACT Droplet‐based triboelectric nanogenerator (TENG) provides a promising route for harvesting low‐frequency ambient mechanical energy. However, the output of solid‐liquid system is still limited by the unclear mechanism of interface charge storage and the lack of effective means to take advantage of bulk‐charges. Here, we introduce a solid‐liquid TENG based on dielectric property modulation, which enhances interfacial charge retention using a substrate with adjustable conductivity. This design enables a single droplet to generate a cumulative 4.2 kV within 15 s, achieving the highest voltage reported for solid‐liquid contact TENGs. Moreover, the creative design of back‐electrode strengthens charge induction at the collection electrodes and suppresses positive‐charge induction at the top electrode, leading positive‐charge to the back electrode for spatially targeted bipolar charge collection and yielding a 5‐fold current increase. According to the strong dependence of output signals on substrate properties, we developed a non‐contact, contamination‐free material‐recognition sensor with millisecond‐level identification. This work elucidates substrate‐selection principles, enables millisecond‐scale material identification, and offers a high efficient energy harvesting strategy for solid‐liquid TENGs.