Hierarchical Assembly of Carbon Dots with Full‐Solar‐Spectrum Absorption for Solar Energy Applications

Carbon dots (CDs) featuring low-cost, non-toxic, and appealing optical properties demonstrate promising applications in energy, e.g. solar energy capture and conversion. However, it remains a significant challenge to expand the absorption bands of CDs from visible to near-infrared (NIR) spectral regions to harness the entire spectrum of sunlight for efficient solar energy utilization. Herein, hierarchical assemblies of CDs (HA-CDs) are constructed by stepwise assembling monodispersed ultraviolet-absorbing CDs to water-soluble visible-NIR absorbing supra-CDs (PA-CDs), and then complexing PA-CDs with Fe³⁺ ions to form 3D porous architectures (HA-CDs) with full solar spectrum absorption and good water resistance. Notably, the HA-CDs exhibit good hydrophilicity and superior photothermal conversion efficiency of 84% under simulated solar irradiation. The facile Fe³⁺ ion cross-linking assembly property enables the in situ preparation of HA-CDs on various fabric substrates, resulting in low-cost, high-performance photothermal conversion products. High-performance 2D solar-driven interfacial water evaporation, electricity generation, and water-electricity cogeneration have been demonstrated in the HA-CDs in situ coated fabric (HA-CDs-fabric). This study provides a novel and effective design approach for the development of high-performance CD-based photothermal materials for solar energy applications.