Dielectric Materials As Optical Emitters for Thermophotovoltaics

Abstract

Thermophotovoltaics (TPV) are a promising route for converting heat generated as a byproduct into usable electricity through a clean energy paradigm. A primary challenge in the field is that the material options used to date for the optical emitters substantially constrain the power conversion efficiency of this process. Thus, we screened the optical response (i.e. permittivity) of >2,800 material combinations with melting point >2,000 oC, comprising refractory silicides, borides, carbides, nitrides, oxides, and metals [1]. Overall, the mismatch in permittivity allowed for emission control, key for the development of high performing TPV. We found a handful of emitters for TPV with theoretical efficiency >60% at 1800 oC, for GaSb solar cells. To complement our analysis, we also identified optimal material combinations for InGaAsSb, InGaAs, Ge, GaSb, and Si photovoltaic devices. The final down selection of materials is also based on their thermal expansion and thermochemical stability, which are frequently overlooked. The discussion of the best material options will be accompanied by the optical characterization of selected materials up to 1500 oC, using in situ reflection and transmission measurements [2]. Finally, we will discuss the specific case of SiC/AlN emitters for the abovementioned photovoltaic options [3].