Miscibility-Controlled Phase Separation in Double-Cable Conjugated Polymers for Single-Component Organic Solar Cells with Efficiencies over 8.

Abstract

In this work, a record power conversion efficiency of 8.40% was obtained in single-component organic solar cells (SCOSCs) based on double-cable conjugated polymers. This is realized based on the finding that exciton separation plays the same important role as charge transport in SCOSCs. Herein, we designed two double-cable conjugated polymers with almost the identical conjugated backbones and electron-withdrawing side units, but the extra chlorine (Cl) atoms had different positions on the conjugated backbones. We found that, when Cl atoms were positioned at the main chains, the polymer formed the twist backbones, enabling better miscibility with the naphthalene diimide side units. This could improve the interface contact between conjugated backbones and side units, resulting in efficient conversion of excitons into free charges. These observations were confirmed by systematical studies via several advanced measurements. These findings reveal the importance of charge generation process in SCOSCs and also suggest a strategy to improve this process, that is, controlling the miscibility between conjugated backbones and aromatic side units in double-cable conjugated polymers.