The application of oxidative chemical vapor deposited (oCVD) PEDOT to textured and non-planar photovoltaic device geometries for enhanced light trapping

Abstract

In organic photovoltaics (OPVs), active layer thicknesses are limited by exciton diffusion length. Thus, non-planar surfaces and device architectures are desired for enhancing the light absorption in OPVs. The oxidative chemical vapor deposition (oCVD) process enables the formation of conformal films of conducting polymers on complex surface structures. oCVD poly(3,4 ethylenedioxythiophene) (PEDOT) is demonstrated to be compatible with a wide range of nano- to macro-scale textured and non-planar architectures that have been demonstrated to enhance light absorption in photovoltaics by various mechanisms of light trapping, such as lengthening optical pathways and taking advantage of reflective light bouncing. Here, conformal oCVD (PEDOT) layers are demonstrated over submicron features including submicron nanowedges and nanocones (with 70–100nm groove depth and 100nm pitch) and square gratings (50–350nm groove depth and 139–833.3nm pitch). In contrast, solution-applied PEDOT:PSS exhibits blanketing, thinning at the top of the features, and welling up of material in the bottom of the features, thus failing to conformally coat the complex surfaces. The application of oCVD PEDOT to macro-scale 3D OPV architectures was also explored. Enhanced active layer absorbance is shown using tetraphenyldibenzoperiflanthene (DBP) as the absorbing layer over the PEDOT.