Current invariant as fundamental relation between saturation currents and band gaps for semiconductor solar cells

Abstract

The optimization of present multijunction junction solar cells and the development of new concepts is an important task for modem photovoltaics. For its development, special attention should be paid to the potential quality of photoactive p-n junctions, as well as to their properties when operating at various temperatures. The present research has shown that for two-diode model of the p-n junction it is convenient to use current invariants Jz1 and Jz2 for calculating the diffusion and recombination saturation dark currents J01 and J02 for p-n junctions based on semiconductor materials with any band-gap energy. It has been experimentally found that Jz1 and Jz2 are constants relating the semiconductor material band gap energy and temperature with J01 and J02. It has also been shown that Jz1 and Jz2 determine the open circuit voltage and the value of voltage offset WOC. Current invariant suggested to be useful tool for evaluating the quality of a p-n junction and for modeling the characteristics of solar cells because it allows making calculations taking into account both main mechanisms of current flow and the operating temperature of the device.