Self-charge pumping circuit with high reverse-voltage diodes for stepwise charge enhancement in stack triboelectric nanogenerators

• Circuit modeling reveals charge pumping mechanism of SCPC in stack TENGs. • High-voltage diodes in SCPC induce excessive charge in stack TENG. • Edge breakdown in uncovered stack TENGs is experimentally investigated. • Corona discharge causes polarity inversion via SCPC diode reverse voltage. • Stepwise charge enhancement boosts TENG output from 50.2 nC to 94.0 nC. Due to the exceptional charge accumulation capability, the self-charge pumping circuit (SCPC) has proven its significant potential in enhancing the performance of triboelectric nanogenerators (TENGs). However, the lack of a theoretical and systematic understanding of the influence of the SCPC parameters on TENGs, particularly the widely adopted stack TENGs, hinders its optimization and broader applicability. This work systematically investigates the performance of the stack TENGs with SCPC in different connections and with different components to understand their roles in charge pumping. An equivalent circuit model is established and simulated to aid the understanding by collaborating with experiments. Simulation and experimental findings show that a high reverse voltage of diodes in SCPC can induce excessive charge accumulation, potentially driving the voltage of stack TENG beyond the corona discharge threshold, leading to unintended charge injection into triboelectric layer. Building upon these insights, a novel stepwise charge enhancement approach is proposed to boost surface charge density in stack TENGs to enhance its outputs. For the fabricated stack TENG, this approach enables a progressive increase in short-circuit transferred charge from 50.2 nC to 69.4 nC, and subsequently to 94.0 nC. Compared to counterparts, proposed approach offers the advantages of safety and simplicity, while allowing the triboelectric charge polarity to be tailored according to practical requirements. Additionally, edge breakdown phenomenon during the pumping process is also observed and systematically investigated through artificial edge breakdown experiment. This work advances the fundamental understanding of the influence of the SCPC on TENGs, and presents a promising method for developing high-performance TENGs with extensive application potential.