Abstract:
One of the promising areas of photovoltaic and heat power engineering is the development of highly efficient photothermovoltaic (FTV) systems for converting the thermal energy of heated bodies into electrical energy. They have important advantages over other thermal power devices. It is known that for many semiconductor devices heating affects negatively their operation but for a photothermovoltaic element it increases its efficiency. In this work we studied the process of the appearance of voltage and electric current in the p-Si - n-(Si2)1-x-y(Ge2)x(ZnSe)y structure at it is uniformly heated both in the dark and in the light. Upon uniform heating of the p-Si - n-(Si2)1-x-y(Ge2)x(ZnSe)y heterostructure, both in the dark by heat and photo heating, and in light by solar radiation an electric current and a potential difference were generated in it. In the studied temperature range the dark current generated by photoheating has three orders of magnitude greater than in the case of thermal heating. However the potential difference generated by photoheating slightly decreases with increasing temperature but its value is almost two orders of magnitude greater than in the case of thermal heating. There is also a slight decrease in the photocurrent and potential difference at increasing temperature. Since the composition of the substrate - film intermediate region changes continuously from Si to the n-(Si2)1-x-y(Ge2)x(ZnSe)y epitaxial film, it is a graded-gap layer with a smoothly varying composition that prevents breaks in the energy zones of the p-n structure . Due to the variability in the intermediate region, an energy barrier arises, mainly for holes, which contributes to the appearance of an additional separating field determined by the gradient of the band gap of this layer. Therefore in this structure the hole current caused by photothermally generated electron-hole pairs can be significant up to higher temperatures. The low efficiency of the studied structure is obviously associated with the recombination of the main parts of the photothermogenerated charge carriers.
|