A Stretchable Bulk-Direct-Current Triboelectric Nanogenerator (BDC-TENG) Enabled by Bulk-Charge Drift in Doped Polymers

Most triboelectric nanogenerators (TENGs) rely on surface electrostatic induction and require external rectification for DC output, introducing energy loss and circuit complexity. Existing DC-TENGs based on semiconductor junctions or ionic media that bypass rectifiers suffer from critically low output voltages (typically < 5 V). Here, we introduce a materials-driven paradigm that shifts TENG design from surface-limited induction to bulk-charge migration. By constructing a percolating conductive network within a doped polymer composite, interfacial triboelectric charges travel directly through the bulk, forming a continuous unidirectional current loop. The resulting device delivers a substantially higher cumulative open-circuit voltage (∼ 88 V per cycle) and a short-circuit current of ∼ 4.1 μA. Demonstrations include significantly enhanced capacitor-charging efficiency compared to rectified conventional TENGs and a self-resetting alarm system based on voltage-cumulative air breakdown. This work establishes a new design route for high-performance DC-TENGs, where material-level control of charge transport unlocks previously inaccessible performance headroom in mechanical energy harvesting.