Synthesis of Alkoxyacene-Based Random Copolymers and Binary Solvent Additive for High Efficiency Organic Photovoltaics

Abstract

The synthesis of three random copolymers-BD2FON-OB30, BD2FON-OB50, and BD2FON-OB70-comprised of different molar ratios of alkoxyphenylene and alkoxynaphthalene is reported by adjusting the ratio of these units for optimized energy levels. When organic photovoltaics are fabricated using these polymers as the electron donor, introduction of the binary solvent additive dramatically enhances power conversion efficiency (PCE) up to 7%, compared to those of the devices without additive (approximate to 2% of PCEmax) and with single additive (approximate to 3% of PCEmax). (without additive: 1-2% and with single additive: 0-3%). These improvements result from minimized bimolecular recombination and balanced electron/hole mobility ratio by optimized bicontinuous D:A morphology in the active layer. Thus, the strategy shows the efficient enhancement of device efficiency by control the morphology using binary solvent additives in the bulk heterojunction film consisting of polymer and fullerene.