Photochromism‐Driven Full Solar Spectrum Absorption for Efficient Photo‐Thermo‐Electric Conversion

Full solar spectrum absorbing photothermal materials may maximally utilize solar energy in emerging photo-thermo-electric conversion technology for outdoor energy harvesting, remote power supply, wearable electronics, and aerospace. However, composite materials with full solar spectrum absorption still suffer from low open-circuit voltages (≤ 200 mV) and limited power densities (≤1 W·m^-2), and single-component materials are subject to insufficient absorption range (< 1100 nm), complicated synthesis process, or expensive precursors. Herein, a readily available viologen-based organic compound with a π-stacked supramolecular structure is found to exhibit full solar spectrum absorption (250-2500 nm) and high near-infrared (NIR) photothermal conversion efficiency (PCE >60%) after electron-transfer photochromism. Integrated with a commercial thermoelectric generator (TEC1-12701), the resulting device achieved an open-circuit voltage of 292.3 mV and a power density of 1.30 W·m^-2 under 1 Sun irradiation. This photochromic strategy provides a new path to achieve efficient photo-thermo-electric conversion.