Fast construction of dianthraceno[a,e]pentalenes for OPV applications
A new method based on a palladium-catalyzed tandem reaction for the fast construction of a dianthraceno[a,e]pentalene (DAP) framework is developed, which gave a series of dianthraceno[a,e]pentalenes with good functional group tolerance, and it should be highlighted that five C–C bonds were formed in one reaction. The photophysical and electrochemical properties of DAP derivatives were examined in detail. Interestingly, cross conjugation can be observed for DAPs substituted with electron-withdrawing substituents, which results in decreased optical bandgaps and the highest occupied molecular orbital (HOMO) energy levels. Because of the good absorption features, high fluorescence quantum yield and appropriate frontier energy levels, dianthraceno[a,e]pentalene with a p-((2-hexyldecyl)-2-cyanoacetate)phenyl group (DAP-PhCA) was utilized for solution-processed bulk-heterojunction solar cells, which delivered a power conversion efficiency of 2.05% with a high open-circuit voltage (Voc) value of 0.95 V.