Controlling the morphology of photoactive layers towards nanoscale bi-continuous donor/acceptor interpenetrating networks is a key issue to build high-performance organic solar cells (OSCs). Due to the distinct properties between donor and acceptor materials, casting an active layer from a single solvent solution usually results in an either insufficient or excessive phase separation that reduces the device performance. In comparison to the fullerene acceptors with closed-cage structures, non-fullerene acceptors which are widely used at present possess anisotropic π–π interactions similar with p-type organic semiconductor donors. While the strategies used for morphology optimization of non-fullerene-based blends empirically follow the treatments originally developed in fullerene-based systems, they are unable to meet the diverse molecular structures and features of the non-fullerene acceptors.
Very recently, Prof. Chaohua Cui and colleagues in Soochow University reported a new morphology controlling approach by utilizing the synergistic effect of dual additives of 4,4′-dimethoxyoctafluorobiphenyl (PFO) and 1-chloronaphthalene (CN).
The strong crystallinity of OFP offers the possibility to restrict the over aggregation of non-fullerene acceptors with high crystallinity during the film cast process, leaving the well-established phase separation with nanoscale bicontinuous donor/acceptor interpenetrating network after OFP volatilization by subsequent thermal annealing treatment.
In particular, the PTQ10:m-BTP-C6Ph-based device processed by the dual additives of CN and PFO showed a remarkable power-conversion efficiency (PCE) of 17.74% associated with a high fill factor (FF) of 0.783, whereas the control device processed by CN yielded a relatively lower PCE of 16.45% with an FF of 0.749. The results demonstrate the promising application of dual additives of OFP and CN in optimizing the morphology of OSCs toward better photovoltaic performances.
See the article: Fan C, Yang H, Zhang Q, Bao S, Fan H, Zhu X, Cui C, Li Y. Synergistic effect of solvent and solid additives on morphology optimization for high-performance organic solar cells. Sci. China Chem., 2021, DOI: 10.1007/s11426-021-1114-3.
Science China Chemistry