Three-dimensional metallo-dielectric selective thermal emitters with high-temperature stability for thermophotovoltaic applications

Abstract

Selective thermal emitters concentrate most of their spontaneous emission in a spectral band much narrower than a blackbody. When used in a thermophovoltaic energy conversion system, they become key elements defining both its overall system efficiency and output power. Selective emitters׳ radiation spectra must be designed to match their accompanying photocell׳s band gap and simultaneously, withstand high temperatures (above 1000K) for long operation times. The advent of nanophotonics has allowed the engineering of very selective emitters and absorbers; however, thermal stability remains a challenge since nanostructures become unstable at temperatures much below the melting point of the used materials. In this paper we explore a hybrid 3D dielectric–metallic structure that combines the higher thermal stability of a monocrystalline 3D silicon scaffold with the optical properties of a thin platinum film conformally deposited on top. We show experimentally that these structures exhibit a selective emission spectrum suitable for TPV applications and that they are thermally stable at temperatures up to 1100K. These structures are ideal in combination with III–V semiconductors in the range Eg=0.4–0.55eV such as InGaAsSb (Eg=0.5–0.6eV) and InAsSbP (Eg=0.3–0.55eV).