Achieving High Power Density and Long-Term Stable Flexible Triboelectric Nanogenerators through Surface Functionalization of High Work-Function Electrode with Cationic Thiol-Based Self-Assembled Monolayer

In this study, a reliable strategy is demonstrated to improve performance and stability of a triboelectric nanogenerator (TENG) by using cationic (11-mercaptoundecyl)-N,N,N-trimethylammonium bromide (MUTAB) self-assembled monolayer (SAM) as the surface modification layer for high work-function (WF) Ag electrode. The thiol head group of MUTAB can form covalent bond to Ag surface, while the positively charged ammonium group can induce favorable surface dipole moment to lower the WF of Ag layer, enabling efficient charge transfer from Ag electrode to polydimethylsiloxane (PDMS) dielectric layer. This strategy is highly compatible with large-area flexible TENG based on solution-processed Ag nanoparticle layer, affording open-circuit voltage (Voc) of 1008 V, short-circuit current (Isc) of 124.9 µA, and power density of 39.4 W m−2. To the best of our knowledge, such remarkable power density represents the highest value ever reported for SAM-modified TENG. Taking advantage of high output characteristics of flexible TENG, 328 light-emitting diodes can be lit up instantaneously. More encouragingly, the resulting TENG also possesses good stability, maintaining ≈96% of its original Voc after 300 000 cycles of continuous testing. The present findings highlight the importance of surface modification with SAM for efficient and long-term stable TENG, which can advance the development of intelligent self-powered systems.