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

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 pi-pi stacking distance of the two polymers. Our work will offer a new strategy to design new double-cable polymers for SCOSCs.

Automated summary

A new semi-flexible linker was developed for single-component organic solar cells, but the decreased charge transporting properties resulted in lower power conversion efficiencies for devices based on the new polymers.