Analysis of Photocurrent Generation within a Schottky-Junction-Based Near-Field Thermophotovoltaic System

Numerous studies have reported performance enhancement of thermophotovoltaic (TPV) systems when an emitter is separated by nanoscale gaps from a TPV cell. Although p-n-junction-based TPV cells have been widely used for near-field TPV systems, Schottky-junction-based near-field TPV systems have drawn attention recently with the advantage of easy fabrication. However, existing studies mostly focused on the generated photocurrent only in the metal side due to the fact that required energy for the metal-side photocurrent (i.e., Schottky barrier height) is smaller than the band-gap energy. Here, we suggest a precise performance analysis model for Schottky-junction-based near-field TPV systems, including photocurrent generation on the semiconductor side by considering the transport of minority carriers within the semiconductor. It is found that most of the total photocurrent in Schottky-junction-based near-field TPV systems is generated in the semiconductor side. We also demonstrate that further enhancement in photocurrent generation can be achieved by reabsorbing the usable photon energy in the metal with the help of a backside reflector. The present work provides a design guideline for Schottky-junction-based near-field TPV systems, taking into account three types of photocurrents.