The power law J–V model of an illuminated solar cell

We have earlier introduced the power law equation, j=1−(1−γ)v−γvm, where j=J/Jsc and v=V/V∝, to simplify determination of the J–V curve, fill-factor and peak power point of an illuminated solar cell from a few measurements as well as physical parameters. However, the validity of the various formulae and parameter extraction procedure was established for a limited class of cells, having moderately convex J–V curves with fill-factors of 0.56–0.77 and obeying single exponential theory with bias independent photocurrent. This paper presents a thorough validation of the model proposed earlier. New formulae and parameter extraction procedure are presented to extend the applicability of the power law equation to a much wider variety of cells. The J–V curves considered in this paper range from concave (fill-factor<0.25) to highly convex (fill-factor>0.85), and their theoretical expressions contain bias dependent photocurrent and double exponential terms. It is shown that the power law equation also simplifies the calculation of the cell bias point for an arbitrary load.