An all-in-one Ag2Se-based flexible solar-thermoelectric generator with photothermal integration

Flexible solar-thermoelectric generators hold great promise for efficient solar energy harvesting and power supply in wearable electronics. However, the achievement of strong photothermal and thermoelectric performance simultaneously within a single material remains a significant challenge. Here, we propose a fully integrated solar-thermoelectric generator that directly employs Ag2Se thermoelectric thin films as the light-absorbing terminal, combined with a bottom infrared-reflective layer and surface visible anti-reflective coating. This multilayer architecture enables solar-selective absorption and enhances the photothermal conversion efficiency of Ag2Se up to 87.6%, while demonstrating good generalizability to other narrow-bandgap thermoelectric films. The resulting ring-shaped flexible generator delivers a maximum temperature difference and power density of 19.6 K and 0.17 μW cm-2 under 1-sun irradiation and exhibits a stable peak output power of ~1 μW under prolonged outdoor sunlight. These results highlight an effective strategy for high-efficiency solar-thermoelectric generators design and broaden the application potential of narrow-bandgap thermoelectric thin films in photothermal energy conversion.