Resistive Effects on the Spatially Resolved Absolute Electroluminescence of Thin-Film Cu(In, Ga)Se2 Solar Cells Studied by a Distributed Two-Diode Model

Electroluminescence (EL) images with absolute photon emissions from Cu(In, Ga)Se2 (CIGS) solar cells were obtained under different forward current injections, with the spatially distributed EL emission becoming non-uniform as the current density gradually increases. A distributed two-diode electrical three-dimensional model was established which simulated the dark current density-voltage curves and the absolute EL images of the CIGS solar cells very well. Then, the resistive effects were analyzed using this model and simulation results show that the sheet resistance of the transparent conductive oxide (TCO) layer dominates the non-uniform distribution of the EL emission in the studied CIGS thin-film solar cells. The effect of the sheet resistance of the TCO and the series resistance of the micro-diode on the EL variations is found to become obvious under high-current-injection conditions, whereas the effect of shunt resistance of the micro-diode on the EL variations becomes more obvious under low-resistance value or low-current-injection conditions.