Achieving Efficient Thick Film All-polymer Solar Cells Using a Green Solvent Additive

Advances in organic photovoltaic technologies have been geared toward industrial high-throughput printing manufacturing, which requires insensitivity of photovoltaic performance regarding to the light-harvesting layer thickness. However, the thickness of light-harvesting layer for all polymer solar cells (all-PSCs) is often limited to about 100 nm due to the dramatically decreased fill factor upon increasing film thickness, which hampers the light harvesting capability to increase the power conversion efficiency, and is unfavorable for fabricating large-area devices. Here we demonstrate that by tuning the bulk heterojunction morphology using a non-halogenated solvent, cyclopentyl methyl ether, in the presence of a green solvent additive of dibenzyl ether, the power conversion efficiency of all-PSCs with photoactive layer thicknesses of over 500 nm reached an impressively high value of 9%. The generic applicability of this green solvent additive to boost the power conversion efficiency of thick-film devices is also validated in various bulk heterojunction active layer systems, thus representing a promising approach for the fabrication of all-PSCs toward industrial production, as well as further commercialization.