Characterization of light-intensity dependence of equivalent-circuit parameters in organic photovoltaic cells via Bayesian estimation

Extracting equivalent circuit parameters from the current-voltage (I-V) characteristics of solar cells using Bayesian estimation enables the unique determination of the ideality factor n, a task that is difficult with the least-squares method. This study shows dependences of the five equivalent circuit parameters based on the 1-diode model of an organic solar cell on light intensity via Bayesian estimation. The dependence is found to be relatively smooth and monotonic for most parameters. The results revealed that the diode ideality factor n increases significantly as the illumination light intensity increases, although the underlying physical mechanisms remain unclear at this stage.