The open-circuit voltage of N+-N-P high-low-emitter (HLE) junction solar cells in concentrated sunlight

Abstract

Simple analytical expression for the open-circuit voltage of a n+-n-p (p+-p-n) high-low-emitter (HLE) junction solar cell, which is valid for both the low and high levels of optical illuminations, is presented. Based on the principle of superposition, the open-circuit voltage of a n+-n-p high-low-emitter junction solar cell is expressed in terms of the short-circuit current density and the known saturated dark current. Effects of the high-low junction, the energy-gap shrinkage, and the dimensions of the HLE junction solar cell on the open-circuit voltage are included. The numerical results of the derived expression are found to be in good agreements with the exact numerical analysis of Sah et al. The optimal design considerations based on the known characteristics of the open-circuit voltage are also discussed.