Hybrid photon-enhanced thermionic emission and photovoltaic converter with concentrated solar power

Photon-enhanced thermionic emission (PETE) converter is a solid-state heat engine, in which hot electrons emit from a p-type semiconductor cathode to an anode across a vacuum gap. Photon-enhanced mechanism reflects in reducing the electron emission barrier by photo-induced quasi-Fermi level splitting. High photon-enhancement mode requires a thin cathode thickness to reduce the recombination of excited-electron during diffusion. Whereas, thin cathode causes huge photon penetration loss. In this work, we propose an original concept of hybrid photon-enhanced thermionic emission converter and photovoltaic (PETE-PV) solar cell. The penetrating solar photons are utilized by photovoltaic sub-devices to yield additional output power. The operating characteristics and superiority of a four-terminal PETE-PV solar cell were demonstrated by simulation. Results show that the solar cell gains a 4-8% point of power conversion efficiency boost thanks to the photovoltaic sub-device. In addition, we developed a PETE prototype with light impinging through a transparent anode (i.e., indium-tin-oxide film) to a cathode surface. Experimental results demonstrate that the cathode saturation current under illumination is similar to 300-fold larger than that of pure thermionic emission mode, and the cathode work function is reduced by 0.6 eV. This study lays a solid foundation for further development and application of PETE-PV solar cells.

Automated summary

Photon-enhanced thermionic emission (PETE) converter is a solid-state heat engine that reduces the electron emission barrier using photo-induced quasi-Fermi level splitting. This study proposes a concept of a hybrid PETE-PV solar cell that utilizes penetrating solar photons to increase output power. Simulation and experimental results demonstrate the superior performance of the PETE-PV solar cell.