Design and Theoretical Study of a Metamaterial Absorber-Emitter Pair Matched with a Low-Bandgap PV Cell for an STPV System

Abstract

The conversion efficiency of conventional semiconductor photovoltaic (PV) devices is restricted to a low level due to the Shockley-Queisser (S-Q) limit. A solar thermophotovoltaic (STPV) system, which consists of a spectrally selective absorber, narrowband emitter, and low-bandgap PV cell, can serve as an alternative to overcome this theoretical limit. However, the stringent requirements of absorber and emitter (like angular and polarization insensitivity and high-temperature resistance) require a careful selection of appropriate material and optimization of structures. To further improve the efficiency of the overall STPV system and ensure high performance, we designed a metamaterial-based absorber-emitter pair matched with InGaAsSb cells for an STPV system. Our numerical simulations demonstrate that the designed absorber provides ultrahigh broadband absorption in the spectral range of 300-2000 nm with a sharp decrease in absorptivity beyond 2000 nm, improving the spectral efficiency to 98%. For the emitter, narrowband emission is ultimately achieved, which prevents both sub-bandgap emission and thermalization loss in the PV cell. Moreover, the pair composed of refractory materials is insensitive to the incident angle and polarization angle. According to detailed balance calculations, the system efficiency can exceed the S-Q limit (41%) since a low temperature (1453 K) and the maximum efficiency (45.94%) outperforms previously reported demonstrations of STPV systems with InGaAsSb cells.