A ring fused N-annulated PDI non-fullerene acceptor for high open circuit voltage solar cells processed from non-halogenated solvents

We report the synthesis and characterization of an arene-fused N-annulated perylene diimide dimer (F-NPDI2) and evaluate the new material's suitability to be used as a non-fullerene acceptor for organic solar cells. Photovoltaic devices were fabricated using the donor polymer PTB7-Th. A direct comparison of bulk heterojunction active layers processed from halogenated and non-halogenated solvent/additive systems was made. Use of the solvent 1,2,4-trimethylbenzene (TMB) and the solvent additive 1,4-dimethylnaphthalene (DMN) led to best power conversion efficiency of ca. 2.5%. Photovoltaic devices had high open circuit voltages upwards of 1.12 V, representing one of the highest for perylene diimide based systems. The active layer morphology and subsequent device performance was insensitive to the nature and volume of solvent additive used for processing and type of coating method (spin vs slot-die) making for a robust bulk heterojunction for large area organic solar cell applications.