Review and tests of methods for the determination of the solar cell junction ideality factors

Up to 22 methods for the determination of the solar cell ideality factor, n, have been presented in this paper. Most of them use the single-exponential diode model, static mode, dc regime, forward bias and a single I–V data set.Mostly, n is estimated simultaneously with other parameters and the methods apply to p–n and/or MS and MIS diodes. The disparities in model assumptions, structures investigated and operation conditions are too large to allow simple comparison of the efficiencies of those methods.Thus, the authors have expressed some considerations on those assumptions and operation conditions, together with comments on strengths and weaknesses of the different techniques. Thirteen methods have been assessed experimentally using a commercial c-Si solar cell. The resulting n values range from 1.26 to 1.50 for the temperature and light intensity intervals of [295; 328] K and [0; 1000] W m⁻², respectively. A discussion on the overall results of this work has also been made, showing notably that (i) the assumption of a constant n for any temperature, light intensity and biasing voltage has been found inappropriate by various workers; (ii) dark condition methods give slightly lower n than light condition ones; (iii) n ranges from 1 to 2 for most of the structures published in this work, except for some MIS structures, hetero-junction semiconductors solar cells, metal contacts with amorphous semiconductors, texturized Si devices, and c-Si (second diode in the two-exponential diodes model); (iv) n, I_s and thus Φ_B for Schottky diodes can be determined by different techniques on dark condition, and may be commonly used as evaluating criteria of metal/semiconductor (MS) and metal/insular/semiconductor (MIS) interfacial properties.