Optical modeling of sunlight by using partially coherent sources in organic solar cells

Abstract

We investigate the effects of coherent and partially coherent sources in optical modeling of organic solar cells. Two different organic solar cells are investigated: one without substrate and the other with a millimeter-sized glass substrate. The coherent light absorption is calculated with rigorous coupled-wave analysis. The result of this method is convolved with a distribution function to calculate the partially coherent light absorption. We propose a new formulation to accurately model sunlight as a set of partially coherent sources. In the structure with glass substrate, the accurate sunlight modeling results in the elimination of coherent effects in the thick substrate, but the coherency in other layers is not affected. Using partially coherent sources instead of coherent sources for simulations with sunlight results in a smoother absorption spectrum, but the change in the absorption efficiency is negligible.

Theory of solar cell light trapping through a nonequilibrium Green's function formulation of Maxwell's equations

“…That is, the current source in the sun is spatially incoherent. On the other hand, it is known that the sunlight is partially coherent [45,46], and that coherence impacts device performance [47,48]. We would like to point out here that our formalism, which builds upon fluctuational electrodynamics, takes spatial coherence into account in a systematic fashion because the field-field correlation of Eq.…”