Polynorbornenes with pendant perylene diimides for organic electronic applications

Abstract

Perylene-3,4,9,10-tetracarboxylic diimides (PDI) have been linked to norbornene through either an imide or a “bay” position. These PDI-functionalised norbornenes are readily polymerised using a ruthenium ring-opening metathesis polymerisation (ROMP) initiator. In one case the polymerisation is shown to be well controlled with a linear dependence of molecular weight on the monomer/initiator ratio. For the polymers with PDI–norbornene linkages through the imide nitrogen, UV-vis spectroscopy suggests significant PDI aggregation both in dilute solution and the solid state, a powder X-ray diffraction peak attributable to π-stacking is seen, and weak n-channel field-effect transistor behavior (electron mobilities <5 × 10−5 cm2 V−1 s−1) was observed. In contrast, the “bay”-linked polymer shows essentially monomer-like UV-vis spectra in both solution and the solid state, no X-ray evidence for π-stacking, and no measurable transistor behaviour. The polymers were used as acceptors in bulk heterojunction solar cells in combination with poly(3-hexylthiophene): low power conversion efficiencies (≤0.38%) were obtained, largely due to low short-circuit currents, again with the “bay”-linked polymer giving the poorest performance.