Broadband and ultrahigh optical haze thin films with self-aggregated alumina nanowire bundles for photovoltaic applications

Optical haze is one of the most important factors to be considered in the development of efficient photonic and optoelectronic devices by manipulating the light behavior. In this work, we fabricated a high optical haze film composed of self-aggregated alumina nanowire arrays and applied this novel structure to improve the energy conversion efficiency of organic photovoltaic (OPV) devices. We controlled the optical properties of films, such as total/diffuse transmittance and haze value, by changing the packing density of nanowires during the wet etching process. By optimizing the etching conditions, the nanowire bundle arrays enabled us to obtain an ultrahigh optical haze value up to similar to 98% or high transmittance up to similar to 96%. By simply attaching the haze film onto the front glass surface of the OPV device, we significantly elongated the optical path length in the active layer, thereby achieving an overall efficiency of 9.01% out of the bare device of 8.17%, resulting in 10.28% enhancement.