Impact of Self-Absorption and Cavity Effects on the Electroluminescence Spectra of Thin-Film Solar Cells

Abstract

Thin-film organic and perovskite solar cells have seen tremendous advances in recent years. A common technique to characterize the low-energy states in these solar cells is electroluminescence spectroscopy. Stemming from their thin film nature, however, the outcoupled electroluminescence spectra of these devices are affected by cavity effects and self-absorption. Herein, a modeling approach is developed taking into account self-absorption, cavity effects, and a nonhomogeneous emission profile, to correct the outcoupled spectrum, thereby yielding the intrinsically emitted spectrum. The modeling approach is then employed to structurally investigate the impact of these effects for a variety of active layer thicknesses, complex refractive indices, device structures, and emission profiles. The data presented uncover trends and provide guidelines that enable gauging the impact of self-absorption and cavity effects on the electroluminescence spectra of a large set of thin-film devices.