Detailed Balance Modeling of Monochromatic Photovoltaic Power Conversion

Abstract

I present detailed balance modeling of photonic power converters, which are photovoltaic devices designed to convert monochromatic light. The detailed balance formalism is standard in finding limiting efficiencies of photovoltaic devices. In this thesis, I discuss both existing theories and original work. I start by discussing optical processes in semiconductors. I reproduce a monochromatic detailed balance model by Martin A. Green, which has stated that monochromatic photovoltaic energy conversion is 100% efficient at infinite input intensity with input photon energy matched to the absorption bandgap. I discuss effects that are not included in this standard model and the existing theories to treat these effects: (1) non-radiative recombination loss, (2) luminescent coupling in multi-layer devices, and (3) light trapping. These background materials are followed by original work, which is divided into three chapters. In these chapters, I present extensions of Green's theory to (1) a single-layer model that includes the effect of incomplete absorption, non-radiative recombination and input photon energy offset from absorption bandgap, and (2) a multi-layer model that includes luminescent coupling and light trapping effects, in addition to the effects already included in the single-layer extension. I show material quality and efficiency improvement predicted for a record-efficiency GaAs PPC. I also predict efficiency for a InAlGaAs device under development that targets conversion at telecommunication wavelength of 1310 nm.