Publications

In this work we provide a systematic scanning tunneling microscopy (STM) study on the self-assembling and mixing behavior of Arylene Ethynylene Macrocycles (AEMs) containing 1,4-phenylene, 1,4-naphthylene or 9,10-anthrylene substituents at the solid/liquid interface. The effect of bulky substituents on the self-assembly structure was investigated and we found that 1,4-phenylene ethynylene macrocycle (AEM-B) and 1,4-naphthylene ethynylene macrocycle (AEM-N) form four and three different patterns at the 1,2,4-trichloride benzene (TCB)/graphite interface, respectively, and a significant concentration effect was observed for both molecules. 9,10-anthrylene ethynylene macrocycle (AEM-A) only forms a filled honeycomb structure at relatively high concentrations. The effect of bulky substituents was attributed to the steric hindrance, which hinders full interdigitation of alkoxy chains. The mixing behavior of binary mixtures of arylene ethynylene macrocycles was also investigated at the TCB/HOPG interface. The results demonstrate that the steric hindrance brought by the bulky groups does not enable sufficient recognition between identical molecules at the interface and random mixing was observed for binary mixtures of AEM-B and AEM-N. The mixing behavior of AEMs could also be predicted by the parameter called the 2D isomorphism coefficient.

An effective method was developed to prepare triphenyleno[1,2,3,4-ghi]perylenediimide derivatives, via ICl-induced annulation, dehalogenation, followed by photocyclization. A perylenediimide (PDI) dimer featuring a terphenyl bisethynylene linker was thereby transformed into a benzo[k]tetraphene fused with two benzoperylenediimides. These PDI derivatives exhibited electron mobility up to 0.079 cm(2) V-1 s(-1) in solution-processed thin film transistors.

Two polymers, r-PDI-diTh and i-PDI-diTh, were synthesized as acceptors applicable for solution-processed BHJ OSCs. By introducing a bulky, dove tailed side chain and thereby suppressing the p-p interactions between perylenediimide units in the backbones of acceptor polymers, more effective phase segregation of these acceptors with a donor polymer (P3HT) was realized. By employing the inverted device configuration to better match the vertical phase separation of donor-acceptor polymers produced by solution processing, undesirable polaron pair recombination was suppressed, and PCE up to 2.17% was achieved from the regio-regular acceptor r-PDI-diTh.

A series of PDI dimers featuring various arylene linkers are developed as electron acceptors in organic solar cells. Using P3HT as the donor, power conversion efficiency of up to 2.3% is achieved with two PDI dimers having spirobifluorene linkers. The results indicate that such non-planar, three-dimensional structures effectively suppress self-aggregation and crystallization of the PDI units, which is favourable for their solar cell performance.