Black diamond doubles efficiency of solar concentration
Within the EU-funded project PROME3THE2US2 (Production method of electrical energy by enhanced thermal electron emission by the use of superior semiconductors), researchers developed a new concept for generating solar electricity that combines conventional photogeneration and thermal energy mechanisms. This process combining both mechanisms is called photon-enhanced thermionic emission (PETE), and is based on the electron thermionic emission. Electrons are excited by photons within silicon at high temperatures. PETE can thus be used as a high-temperature topping cycle to further increase efficiency of solar thermal devices. Researchers successfully developed a new solid-state conversion structure that can efficiently convert solar radiation into electrical energy. The system consists of a radiation-absorbing cathode that exploits solar visible radiation for direct photoelectronic generation as well as solar infrared radiation for heat. It thus breaks the emission process into internal PETE and external emission into vacuum. A specifically designed inter-electrode spacing separates the cathode from a low-work-function anode. The work function – the energy needed to remove an electron from a solid – of the anode was even lower than that of the cathode to maximise the electron flow and thus the conversion efficiency. The team exploited black diamond for use in the cathode electrode. This material can endure high temperatures and efficiently emit electrons in addition to effectively absorbing photons at temperatures up to 1 000 °C. Furthermore, the team added impurities to black diamond to improve performance. PROME3THE2US2 contributed to the delivery of highly efficient solar conversion able to meet the world's energy needs. Based on the innovative solid-state structures and black diamond, the technology can double the efficiency limits of common photovoltaics today. In addition, this exciting low-cost material can also be exploited for other electronic applications outside solar technology.
Keywords
Black diamond, solar concentration, PROME3THE2US2, electrical energy, photon-enhanced thermionic emission
