Ultrablack, Harsh-Condition-Resistant Micro-Pyramid Graphite Array for Solar Energy Harvesting and Conversion

Efficient solar energy utilization demands high-absorption materials that are low-cost, easy to fabricate, and harsh-condition-resistant. Herein, the micro-pyramid graphite array (GA) is fabricated by nanosecond laser etching followed by surface modification with the antireflection layer. The optimized GA exhibits a high solar absorbance of 99.3% and good omnidirectional broadband absorption. The superblackness is ascribed to several combined effects, including: the light-trapping effect of micro-pyramid cones, the enhancement of localized electric field around submicron/nano-wrinkles, as well as the reduced interfacial reflection via a low-refractive-index polymer coating. With its superior thermal stability, the GA can convert the high-irradiance light into heat, reaching the surface equilibrium temperature of 300°C under 10-sun irradiation. The GA-enhanced thermoelectric generator significantly increases the output power density to 20 mW cm^-2 under 10-sun irradiation, which outperforms the reported organic ultrablack materials. The GA may be a promising photothermal converter under harsh operation conditions.