The author begins with an Introduction in which he discusses basic concepts, recent developments, potential advantages offered by TPV systems and a historical background. He then provides a background in blackbody radiators and examines selective and rare-earth oxide radiators. He discusses modelling, fabrication and characterization of TPV convertors, particularly those based on GaSb and InGaAs. He examines the several approaches to recirculating the sub-bandgap photons and ends with a section on modelling of TPV system performance, and conceptual designs and demonstration of TPV systems, including solar powered, biofueled nuclear-fueled, liquid hydrocarbon-fueled, diesel-fueled, propane fueled, and natural gas fueled TPV systems.

A review of progress in thermophotovoltaic generation of electricity

A high temperature thermophotovoltaic (TPV) system is modeled and its system level performance is assessed in the context of concentrated solar power (CSP) with thermal energy storage (TES). The model includes the treatment of the emitter and the heat transfer fluid that draws thermal energy from the TES, which then allows for the identification and prioritization of the most important TPV cell/module level properties that should be optimized to achieve maximum performance. The upper limiting efficiency for an idealized system is then calculated, which shows that TPV with TES may one day have the potential to become competitive with combined cycle turbines, but could also offer other advantages that would give CSP an advantage over fossil based alternatives. The system concept is enabled by the usage of liquid metal as a high temperature heat transfer and TES fluid. The system concept combines the great economic advantages of TES with the potential for low cost and high performance derived from TPV cells fabricated on reusable substrates, with a high reflectivity back reflector for photon recycling.

Thermophotovoltaics: a potential pathway to high efficiency concentrated solar power

Liquid-phase epitaxy of low-bandgap III-V antimonides for thermophotovoltaic devices

Back surface reflectors have the potential to improve thermophotovoltaic (TPV) device performance though the recirculation of infrared photons The “hybrid” back‐surface reflector (BSR) TPV cell approach allows one to construct BSRs for TPV devices using conventional, high efficiency, GaInAsSb‐based TPV material The design, fabrication, and measurements of hybrid BSR‐TPV cells are described The BSR was shown to provide a 4 mV improvement in open‐circuit voltage under a constant short‐circuit current, which is comparable to the 5 mV improvement theoretically predicted Larger improvements in open‐circuit voltage are expected in the future with materials improvements

/pdf/hybrid-back-surface-reflector-gainassb-thermophotovoltaic-2uyn85fug2.pdf

Hybrid Back Surface Reflector GaInAsSb Thermophotovoltaic Devices

Liquid phase epitaxy (LPE) is a growth technique that can be suitable for photovoltaic applications regarding its simplicity and its capacity to produce high-quality thin film. The growth of Silicon proceeds from a molten solution (metal + Si), which is slowly cooled. Temperature range is typically 700–1,000°C and growth rate can be as high as 1 μm min-1. In this chapter, we first introduce the fundamental principles of LPE and then we discuss on the influence of the metallic solvent (In, Sn, Cu, Al …), the temperature range on the growth rate and on the quality of the epitaxial layers. We also review epitaxial growth on polycrystalline silicon or foreign substrates. We finally discuss the development of high throughput LPE deposition equipment.

Liquid Phase Epitaxy

We survey and assess new concepts for “next-generation” GaSb-based thermophotovoltaic (TPV) devices. The objectives are new device structures with novel back mirror designs to better utilize photon recycling effects, isolation schemes to realize monolithic, series-interconnected TPV arrays, and reduced cost by the use of surrogate substrates in place of GaSb or InAs wafers. The processes considered include 1. liquid-phase epitaxial lateral overgrowth on patterned, masked substrates, 2. epitaxial film transfer or wafer fusion techniques, 3. epitaxial growth of GaSb alloys on high resistivity (lattice matched) ZnTe, 4. realization of semi-insulating III-V antimonides, 5. selective wet oxidation of Al-containing antimonides (e.g., AlAsSb) wherein a the semiconducting epitaxial layer is converted to Al2O3 to form a buried insulating layer, and 6. GaSb- and InAs-on-silicon heteroepitaxy.

New concepts for III-V antimonide thermophotovoltaics

Equipment and Instrumentation for Liquid Phase Epitaxy

Optical cavity light-emitting diode structures with 'buried' mirrors, and their fabrication by lateral epitaxy are described. Single-crystal, high-quality epitaxial layers are formed over substrates coated with patterned, reflective masks using liquid-phase or vapor-phase epitaxial lateral overgrowth processes. The reflecting mask acts as a backside mirror and forms an optical cavity leading to enhanced external quantum efficiencies. An AlGaAs optical cavity LED incorporating a refractory metal 'buried' mirror is assessed: a greater than 3-fold increase in output optical power is measured compared to control devices with no buried mirror. Application of the epitaxial overgrowth techniques to LED structures utilizing electron-beam deposited dielectric/semiconductor 'buried' mirrors and to other semiconductor materials, such as InGaAsSb, SiC, and ZnSe is described.

James B. McNeely

Papers

New concepts for III-V antimonide thermophotovoltaics

Equipment and Instrumentation for Liquid Phase Epitaxy

Resonant cavity LEDs by lateral epitaxy