Analysis On The Performance Of The GaSb Cell And Thermophotovoltaic System Under The Near-field Radiation

Near-field thermophotovoltaic is a thermoelectric conversion technology that can increase the system output power density by narrowing the distance between the radiator and the photovoltaic cell based on the macro thermophotovoltaic.The temperature of the photovoltaic cell(the core component of the near-field thermophotovoltaic system)rises sharply under the influence of near-field effect,which leads to the decrease of system's output power density.This paper takes GaSb cell as the research object so as to explore the changes of the performance of the thermophotovoltaic cell under near-field radiation,and analyze its influence on the performance of thermal photovoltaic system.The effects of the distance(between the radiator and the photovoltaic cell),the temperature of the radiator and the convection heat transfer coefficient on the temperature of the photovoltaic cell were analyzed by building energy transmission model of near-field thermophotovoltaic system.The carrier lifetime,the carrier mobility rate,and the intrinsic carrier concentration were analyzed according to the variation of temperature of the photovoltaic cell.It turns out that the carrier lifetime and the mobility rate would decrease,while the intrinsic carrier concentration would increase as the temperature rises.From the changes of these cell parameters,the actual performance of the thermophotovoltaic system was explored considering the influence of the cell temperature.The results are as follows:under the circumstance that the radiator temperature is 2000K,while the distance between the radiator and the cell is 12nm and the cooling system is in the best current condition(which means the convection heat transfer coefficient is 6.5×104 W/(m2·K),the temperature of the photovoltaic cell is 473K,which is higher than the assumed value of 300K in the literature.At this time,the output power density is 237.46W/cm2,which is much lower than 340W/cm2,the density under the assumed cell temperature of 300K.The reason is that when the temperature of the photovoltaic cell increases,so does the intrinsic carrier concentration.It leads to the increase of the reverse saturation current density and the decrease of the open circuit voltage.As a result,the output power density decreases ultimately.In addition,the results reveal that both the reduction of distance between the radiator and photovoltaic cell and the rise of the radiator temperature can result in the increase of output power density with the temperature of the photovoltaic cell rising at the same time.The lower the convection heat transfer coefficient is,the larger range of the increase of the tell temperature would be.In other words,the temperature of the photovoltaic cell is higher under the same distance between the radiator and the cell or the same radiator temperature.Moreover,as the temperature of the photovoltaic cell increases,both the output power density and the system efficiency decrease.Under the circumstance that the radiator temperature is 2000K with the heat transfer coefficient increasing from 6×103W/(m2·K)to 6.5×104W/(m2·K),the minimum distance between the radiator and the cell would decrease from 58nm to 12nm,the output of the system increase from 6.741W/cm2 to 237.47W/cm2,and the system efficiency would increase from 0.068 to 0.158.With the increase of the convection heat transfer coefficient,the performance of the cooling system improves continuously.In conclusion,when the near-field effect is excited by reducing the distance between the radiator and the cell or increasing the radiator temperature in the near-field thermophotovoltaic system,it's necessary to adjust the cell temperature through the cooling system so as to avoid the negative effects of the system performancethe caused by excessive rise of the cell temperature.