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

## TL;DR

A new material absorbs the full solar spectrum and converts sunlight into electricity efficiently using a thermoelectric generator.

## Contribution

A viologen-based compound with photochromism enables full solar absorption and efficient photo-thermo-electric conversion.

## Key findings

- The compound achieves full solar spectrum absorption from 250–2500 nm.
- It reaches a near-infrared photothermal conversion efficiency of over 60%.
- The device outputs 292.3 mV and 1.30 W·m−2 under 1 Sun irradiation.

## 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.

After electron‐transfer photochromism, a black viologen‐based organic compound shows full solar spectrum absorption (250–2500 nm) and near‐infrared photothermal conversion efficiency (NIR‐PCE) >60%. Integrated with a thermoelectric generator, it outputs 1.17 V under 4 Suns irradiation, enough to drive a small fan via photo‐thermo‐electric conversion.