Effect of azomethine donor group on the properties of flexible bulk heterojunction with alkyl perylene diimide acceptor

This paper reports about bulk heterojunctions layers containing azomethine oligomers based on carbazole (AzC) or triphenylamine (AzPA) donor and alkyl perylene diimide derivative (PTCDI-12C) acceptor blended in different weight ratios (1:2), (1:3) and (1:4), prepared by Matrix Assisted Pulsed Laser Evaporation (MAPLE) on flexible substrate of polyethylene terephthalate (PET) covered by ITO. The effect of the type of azomethine donor substituent group and mixed layer composition on the optical and electrical properties was investigated in correlation with the molecular aggregation particularities and surface topographical particularities of the layers.The strong absorption band between 400 and 650 nm was favored by the strong polarization interactions in the layers deposited by MAPLE from chloroform and the red shift of the UV–Vis absorption peaks of PTCDI-12C in the both types of bulk heterojunction layer confirmed the generation during the deposition mostly of J-aggregates, which are associated with the fluorescence emission.The correlation between the roughness, statistical analysis parameters obtained by height-to-height correlation function, grains shape and electrical behavior was analyzed. The samples prepared with AzC donor showed photoelectric behavior with the best parameters for AzC:PTCDI-12C in a weight ratio of (1:3), while the sample with AzPA:PTCDI-12C mixed layer showed an injection contact behavior with the best current (10−4 A for voltage < 0.5 V) at a weight ratio of (1:2). Thus, the behavior of the heterostructures is affected by the type of azomethine: carbazole-azomethine can be potential candidates for optoelectronic applications while triphenylamine-azomethine for electronic application.