Funneling excitation energy toward lower energy excited
states
is a key concept in photosynthesis, which is often realized with at
most two chemically different types of pigment molecules. However,
current synthetic approaches to establish energy funnels, or gradients,
typically rely on Förster-type energy-transfer cascades along
many chemically different molecules. Here, we demonstrate an elegant
concept for a gradient in the excited-state energy landscape along
micrometer-long supramolecular nanofibers based on the conjugated
polymer poly(3-hexylthiophene), P3HT, as the single component. Precisely
aligned P3HT nanofibers within a supramolecular superstructure are
prepared by solution processing involving an efficient supramolecular
nucleating agent. Employing hyperspectral imaging, we find that the
lowest-energy exciton band edge continuously shifts to lower energies
along the nanofibers’ growth direction. We attribute this directed
excited-state energy gradient to defect fractionation during nanofiber
growth. Our concept provides guidelines for the design of supramolecular
structures with an intrinsic energy gradient for nanophotonic applications.