Enhancement of light absorption by using light scattering and emitting dyes in organic photovoltaics

To enhance the power conversion efficiency of organic photovoltaics (OPVs), sufficient light absorption in the active layer is necessary to generate a greater number of excitons. We propose incorporating luminescent dyes into hole transport layer of OPVs as a route of enhancing light absorption, minimizing changes in the morphology and structure of the active layer; dyes scatter incoming collimated light isotropically, thereby increasing the distance light travels in the active layer, which leads to enhanced light absorption. In addition, dyes can absorb light in the portion of the spectrum where the active layer is transparent and re-emit light in the portion of the spectrum corresponding to the absorption peak of the active layer. Coumarin 102 (C102) is a dye that has an absorption wavelength of 389nm, which corresponds to the weakest absorption region of P3HT:PCBM blends. C102 is then able to isotropically re-emit visible light, in the region that corresponds to the absorption spectrum of P3HT, into the active layer. Based on this effect, we demonstrate that the short circuit current density can be increased by 22.8% compared to the reference sample without any dye.