Bismuth oxyhalide based photo-enhanced triboelectric nanogenerators

Utilizing wide absorption characteristics of a narrow bandgap (~1.8 eV) semiconductor, we report on Bismuth Oxyiodide (BiOI) based photo-enhanced triboelectric nanogenerator (TENG). The potentiostatic deposition of tribo-positive BiOI on transparent, electrically conducting Fluorine doped Indium Tin Oxide (FTO) substrates provides a pathway to exploit concurrently the photo-enhanced charge generation and triboelectric effects. When utilized against tribo-negative polydimethylsiloxane (PDMS) films, under illumination, the BiOI/PDMS TENGs’ output was significantly enhanced, wherein an increase of 21% in output voltage, 38% in charge density (26% in short-circuit current density), and 74% in overall power density (from 0.25 Wm−2 (in dark) and 0.44 Wm−2 (under illumination)), respectively, was observed. Correspondingly, a dramatic enhancement (from ~25 mV to ~300 mV) in the average surface potential, termed as surface photovoltage (SPV), for the illuminated BiOI was observed by Kelvin Probe Force Microscopy (KPFM). For an isolated, grounded BiOI/FTO electrode, this enhanced SPV was slow-decaying (~3.5 h) and is attributed to the high dielectric constant, presence of deep surface states and traps within BiOI, and slow charge-exchange with the ambient environment. The work thus not only provides an approach for the enhancement of mechanical-to-electrical efficiency of TENGs by light absorption but can also be utilized for self-powered detection of electromagnetic radiation and photodetectors.