Closed-form model for the open circuit voltage of solar cells with shunt resistance, bias-dependent photocurrent and double exponential terms

Abstract

The parasitic shunt resistance, bias dependence of the photocurrent and phenomena causing a second exponential term in the current density ( J )-voltage ( V ) equation reduce the open circuit voltage, V oc , of illuminated solar cells below the ideal value predicted by the J - V equation having only a single exponential term. This study reports an approximate closed-from solution of the transcendental V oc equation which directly reflects these losses. The solution estimates V oc as a weighted parallel combination of the limiting V oc values corresponding to the domination of one of the several terms of the V oc equation. The solution allows quick design calculation of the V oc of a wide variety of cells in terms of all physical parameters, and provides insight into the influence of losses owing to various factors.