Simulations of Gallium Antimonide (GaSb) p-B-n Thermophotovoltaic Cells
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Simulations of Gallium Antimonide (GaSb) p-B-n Thermophotovoltaic Cells Dante F. DeMeo1 and Thomas E. Vandervelde1* 1
The Renewable Energy and Applied Photonics Laboratories, Department of Electrical and Computer Engineering, Tufts University Medford, MA 02155, U.S.A. * Contact Author: [email protected] ABSTRACT The focus of this paper is the characterization of novel thermophotovoltaic (TPV) cell designs which employ a monovalent barrier layer in the p-n junction. The use of a barrier layer enables these cells to operate at longer wavelengths, higher efficiencies, and higher operating temperatures. Initial designs have been made using gallium antimonide (GaSb), which is one of the more common TPV materials. Simulations were performed using Sentaurus by Synopsys to determine barrier materials as well as to optimize the cell. The p-B-n cell was then compared to a simple p-n junction. The simulations show that a p-B-n cell outperforms a typical p-n junction. Additionally, we expect to see increased performance differentials from this device structure when moving to longer wavelength devices. INTRODUCTION Thermophotovoltaics is a technology which converts radiated heat directly into electricity. Thermophotovoltaic devices follow the same principles as photovoltaic solar cells; the main differences are that TPV focuses on the infrared regime of the electromagnetic spectrum and that TPV systems use different forms of spectral control, such as an emitter and filter, to increase the efficiency of the TPV cell and system.1 These components add benefits such as decoupling the radiation source from the photovoltaic diode, which allows for greater material freedom and also recycling reflected photons from the cell. Reflected photons can be re-absorbed and subsequently re-emitted by the emitter component. As a result of the spectral control and narrow band gaps typically used in TPV devices, they have a considerable advantage in that they are able to use a myriad of heat sources to create energy. One of the most common materials for a TPV diode is gallium antimonide (GaSb), which can readily convert energy from heat sources with temperatures as low as 1700°C due to its bandgap of 0.725eV at room temperature.2 There are many thermal sources of energy of which GaSb would only be able to capture the smallest high-energy portion of the black body spectrum, and as such, there is great interest in creating TPV devices which can absorb lower temperature radiation, while still maintaining operation at around room temperature or above. This type of optimization is one focus of our lab and we have performed such optimizations on other devices and material systems before3-6. Material and recombination problems arise due to the narrow bandgaps required for absorption in the infrared. This is partially due to the large number of intrinsic carriers. The barrier design was first proposed for use with photodetectors7 and has shown considerable success8; however, here we propose using it with photovoltaics in order to suppress recombinati
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