Radiator Tailoring for Enhanced Performance in InAs-Based Near-Field Thermophotovoltaics

TL;DR

This paper presents an optimized InAs-based radiator design for near-field thermophotovoltaics, significantly improving spectral efficiency and power density by revising the dielectric model and tailoring the radiator to the PV cell.

Contribution

It introduces a revised InAs dielectric model based on impurity scattering and demonstrates a nearly threefold efficiency improvement with InAs radiator and cell pairing.

Findings

Revised InAs dielectric model reduces overestimation of free carrier absorption.

Optimized radiator enhances spectral efficiency by nearly three times.

InAs radiator and cell pairing reduces thermal transfer while maintaining power.

Abstract

Near-field thermophotovoltaics (NFTPV) systems have significant potential for waste heat recovery applications, with both high theoretical efficiency and power density, up to 40% and $11 \ \mathrm{W/cm^{2}}$ at 900 K. Yet experimental demonstrations have only achieved up to 14% efficiency and modest power densities (i.e., $0.75 \ \mathrm{W/cm^{2}}$). While experiments have recently started to focus on photovoltaic (PV) cells custom-made for NFTPV, most work still relies on conventional doped silicon radiators. In this work, we design an optimized NFTPV radiator for an indium arsenide-based system and, in the process, investigate models for the permittivity of InAs in the context of NFTPV. Based on existing measurements of InAs absorption, we find that the traditional Drude model overestimates free carrier absorption in InAs. We replace the Drude portion of the InAs dielectric function with a revised model derived from ionized impurity scattering. Using this revised model, we maximize the spectral efficiency and power density of a NFTPV system by optimizing the spectral coupling between a radiator and an InAs PV cell. We find that when the radiator and the PV cell are both made of InAs, a nearly threefold improvement of spectral efficiency is possible compared to a traditional silicon radiator with the same InAs cell. This enhancement reduces subgap thermal transfer while maintaining power output.