Enhanced Energy Harvesting and Human–Machine Interaction Sensing via the Tribo-Photovoltaic Effect in a Metal/n-Type GaAs Triboelectric Nanogenerator

This study presents a novel photovoltaic triboelectric nanogenerator (PTENG) that operates on sliding contacts between n-type (gallium arsenide) GaAs and metal electrodes in the presence of periodic light illumination, which offers harvesting energy synergistically by integrating both photovoltaic and triboelectric effects to enhance the energy output. Using an in-house built test setup with provision of laser illumination, the open-circuit voltage (VOC) and short-circuit current (ISC) were measured for the n-GaAs semiconductors with different metal contacts (Al and Cu). Under both laser light (630 nm) and without laser light conditions, n-GaAs with aluminum contacts exhibited the highest VOC and ISC values, reaching up to 11.2 from 9.0 V and 9.5 from 6.2 μA. The Voc and ISC values with the copper contact were improved to 6.6 from 4.0 V and 4.3 from 2.5 μA under laser illumination and no laser illumination conditions. The photovoltaic effect contributed more significantly than triboelectrification to the output, with electron-hole pairs generated under light further increasing VOC and ISC in alignment with triboelectric charges. Atomic force microscopy and Kelvin probe force microscopy revealed a contact potential difference of 10 mV under laser exposure, confirming enhanced charge separation. The optimized PTENG achieved a maximum power density of 6.8 W/m2 at a 100 kΩ load, which was sufficient to power multiple light-emitting diodes (LEDs) and effectively charge a 1.0 μF capacitor. Performance improvements were further supported by increased sliding speed and larger contact areas. This work demonstrates the potential of PTENGs that combine triboelectric and tribo-photovoltaic effects for efficient and practical energy-harvesting applications.