Analytical method for the analysis of thin SiGe/Si solar cells with front surface field

Abstract

The present paper reports on a simulation study carried out to determine and optimize the effect of the high-low junction emitter (n+/n) of thin film SiGe/Si solar cell. The model is based on a simple analytical approach that draws on relevant device physics, including effective surface recombination velocity at the high-low junction and band discontinuities associated with heterojunctions. The collection of the light absorbed by the front surface field is discussed and an analytical solution is derived for the light-generated current in this layer. The photovoltaic parameters of SiGe/Si solar cells and those of the conventional cell Si/Si are compared. The findings revealed that the addition of Ge ~ 15 % to crystal Si highly enhances short-circuit current density and cell efficiency, whereas the SiGe band-gap degrades particularly the open-circuit voltage. The results also indicate that the solar cell maximum efficiency increase by about 1.7 % when the interface state density is lower than 1011 cm–2.