3D network acceptor with gradient hydrogen bond interaction as a bifunctional layer in quasiplanar heterojunction organic solar cells

Abstract

Quasiplanar heterojunction (Q-PHJ) architecture has been used successfully in organic solar cells (OSCs) with excellent stability. The donor and acceptor layers in Q-PHJ films are usually sequentially spin-coated with orthogonal solvent to maintain their independence. Sometimes it may be difficult to find a completely orthogonal solvent to fabricate Q-PHJ film, on the other hand, the solvent of the upper solution would swell and erode the lower film. In this study, we manipulated intermolecular hydrogen bonds to synthesize three molecules with graded hydrogen bond interactions. A desired layer of hydroxylated BTIC-OH-δ was introduced as a bifunctional layer in Q-PHJ film. The inserted BTIC-OH-δ layer could effectively protect the donor layer from erosion by the upper acceptor chloroform solution, resulting the cascade energy levels in the Q-PHJ OSCs with a high efficiency of 17.33%. Based on the same Q-PHJ film, the prepared semi-transparent device can also achieve an efficiency of 13.44% with AVT of 23.62%. Importantly, this device showed greatly enhanced stability compared to its control device. This work indicates that the hydroxylated molecules with appropriate intermolecular interactions could simply fabricate Q-PHJ devices as a bifunctional layer, and provides a direction for development of efficient and stable Q-PHJ OSCs.