Demonstrating black-diamond-based high-temperature solar cells

<h2>Summary</h2> Efficient high-temperature solar cells are feasible through the photon-enhanced thermionic emission (PETE) mechanism. The development of defect-engineered black-diamond layers, combined with micro-graphitized electrodes fabricated within p-type/intrinsic structures, represents the key technology for sunlight interaction of 0.3-eV electron-affinity PETE diamond cathodes, characterized by excellent electron emission. The resulting PETE converters demonstrate energy generation under concentrated radiation. At operating temperatures ranging from 600 to 900 K, the PETE operational regime is revealed, whereas photoemission and thermionic emission are found to be predominant at lower and higher temperatures, respectively. Cathode thickness emerges as the primary factor limiting the present performance of black-diamond technology. The generation-recombination analytical model applied to the device allows predicting a quantum efficiency of 30.3% for a 300-nm-thick black-diamond cathode operating at 700 K, today attainable with advanced diamond membrane technologies, and a solar-to-electric conversion efficiency of 14.5% for the resulting PETE converter.