Use of Side-Chain Incompatibility for Tailoring Long-Range p Heterojunctions: Photoconductive Nanofibers Formed by Self-Assembly of an Amphiphilic Donor-Acceptor Dyad Consisting of Oligothiophene and Perylenediimide

摘要

To tailor organic p hetero-junctions with molecular-level precision, a rational design strategy using side-chain incompatibility of a covalently connected donor-acceptor (D-A) dyad has been successfully carried out. An oligothiophene-perylenedi-imide dyad, when modified with tri-ethylene glycol side chains at one terminus and dodecyl side chains at the other (2_(Amphi)), self-assembles into nanofibers with a long-range D/A hetero-junction. In contrast, when the dyad is modified with dodecyl side chains at both termini (2_(Lipo)), ill-defined micro-fibers result. In steady-state measurements using microgap electrodes, a cast film of the nanofiber of 2_(Amphi) displays far better photoconducting properties than that of the microfiber of 2_(Lipo). Flash-photolysis time-resolved microwave conductivity measurements, in conjunction with transient absorption spectroscopy, clearly indicate that the nanofiber of 2_(Amphi) intrinsically allows for better carrier generation and transport properties than the microfibrous assembly of 2_(Lipo).