Written by: Leonard Parker | Solar News | 07th November
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 p-p 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.
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