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

Abstract 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.