Incorporating semiflexible linkers into double-cable conjugated polymers via a click reaction

Abstract

Single-component organic solar cells (SCOSCs) have been recognized as a promising photovoltaic technology due to their excellent stability, but their power conversion efficiencies (PCEs) are far lagging behind those of the bulk-heterojunction counterparts. Current strategies have mainly focused on new polymer backbones and pendent acceptors, while linkers are ignored. Here, we develop a new semiflexible linker consisting of a triazole unit and an alkyl chain via a Click reaction between alkyne and azide end groups, which is different from the alkyl linkers in previous reports. Two new polymers, P1 and P2, with different linker lengths (C₆H₁₂-triazole for P1 and C₁₂H₂₄-triazole for P2) were developed. The optical properties, energy levels, photovoltaic performance and morphology of the two polymers were systematically studied and compared with those of a similar alkyl chain linked polymer JP02. Unfortunately, both polymer-based SCOSC devices exhibited low PCEs due to the lower short-circuit current density (J_sc) and fill factors (FF) than those of the JP02 based cells, which may be ascribed to the decreased charge transporting properties originated from the increased π–π stacking distance of the two polymers. Our work will offer a new strategy to design new double-cable polymers for SCOSCs.