Solar cell temperature dependent efficiency and very high temperature efficiency limits
Abstract
Clean renewable solar energy is and will continue to be a critically important source of electrical energy. Solar energy has the potential of meeting all of the world's energy needs, and has seen substantial growth in recent years. Solar cells can convert sun light directly into electrical energy, and much progress has been made in making them less expensive and more efficient. Solar cells are often characterized and modeled at 25 °C, which is significantly lower than their peak operating temperature. In some thermal concentrating systems, solar cells operate above 300 °C. Since increasing the temperature drastically affects the terminal characteristics, it is important to quantify the losses caused by raising the temperature. Methodologies for including the temperature dependent material parameters in analytical and detailed numerical models have been examined. The analytical model has been developed to analyze Shockley-Queisser detailed balance limit, as well as the Auger, Radiative and SHR recombination limiting cases from 25 °C to 800 °C, at 1x, 500x and 2000x suns concentrations. The results of this analysis show that the efficiency of a direct bandgap material with an optimal bandgap could reach 19 % at 400 °C and 2000x suns, if the SHR recombination is reduced to an acceptable level. An analytical solar cell model was also used in a quasi-3D numerical model to simulate the temperature dependent resistivity losses. It was found that the resistive losses can double when the temperature of a solar cell increases from 25 °C to 100 °C. This will cause the conversion efficiency temperature coefficient to deteriorate by 10%. By using the temperature dependent material parameters for Si in a detailed numerical model, it was found that some of the adjustable parameters, such as the base thickness, increase the conversion efficiency temperature coefficient and the Voc, while other parameters would only increase the Voc. This conclusion can be used by solar cell manufactures to improve the solar cell parameters with the biggest possible gain in device performance.
Degree
Ph.D.
Advisors
Gray, Purdue University.
Subject Area
Electrical engineering|Nanotechnology|Energy
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