Effects of Incoherent Front Cover Glass on Current-Voltage Characteristics of Cu(In,Ga)Se2 Solar Cells: Investigation into Calculation Accuracy for Cover Glass Modeled as Optically Coherent or Incoherent

We numerically investigate the effects of an incoherent front cover glass on the current–voltage (J–V) characteristics of a Cu(In,Ga)Se2 (CIGS) solar cell using an integrated optoelectronic model. A 3-mm cover glass—the thickness of which was larger than the coherence length of sunlight—was incoherently modeled based on the equispaced thickness averaging method, where coherent simulation results of the wave equation were averaged over a set of equispaced phase thicknesses. The changes in optical power dissipation, absorptivity and electron–hole pair generation rate were calculated depending on the variation of the equispaced phase thickness. The calculation results of the J–V curves were obtained through numerical solutions of the coupled Poisson and continuity equations. By comparing the J–V curves calculated between coherently and incoherently modeled cover glass, we obtained a maximum ±0.54% deviation of the short-circuit current density. This demonstrates that the front cover glass should be modeled as optically incoherent to improve the calculation accuracy of the electrical J–V curves as well as the optical absorption characteristics in the optoelectronic modeling of CIGS solar cells.