Engineered periodic conical absorbers achieving near-unity solar absorption for energy harvesting

• Design and fabrication of PCA using CNC-drilled template replication. • 99.51 % solar absorptance from visible to near-infrared by engineered PCA. • 71.39 % photothermal conversion efficiency under one-sun irradiation. • PCA-based STEG system delivers 405 μW cm −2 output power. • Demonstrated resistance to thermal shock, corrosion and mechanical deformation. Broadband high-absorption materials are essential for practical applications in solar energy harvesting. The fabrication of these materials typically relies on the construction of cavity structures to enhance light absorption. However, achieving near-unity broadband absorption while maintaining precise cavity control, enabling large-area fabrication, and ensuring process simplification remains a critical challenge. This study designs cavity-structured absorbers and utilizes ray-tracing simulations to investigate the effects of cavity shape and geometric parameters on the absorptance of absorbers. Computer numerical control (CNC) drilling was innovatively combined with template replication methods to fabricate a periodic conical absorber (PCA) featuring precisely controlled cavity structures that are scalable for large-area production. The engineered conical cavity structures of the PCA achieve an integral absorptance of 99.51 % across the visible to near-infrared spectrum. Under one-sun irradiation, the PCA exhibits highly efficient solar energy absorption, with the surface temperature rising to approximately 88 °C, corresponding to a photothermal conversion efficiency of 71.39 %. Furthermore, the PCA-based solar thermoelectric generator (STEG) system delivers an ultrahigh output power of 405 μW cm −2 . Additionally, the PCA demonstrates strong resistance to thermal shock, corrosion, and mechanical deformation, fulfilling the requirements for solar energy harvesting and utilization.