Nanoscale spatial extent of photogenerated polarons in regioregular poly(3-octylthiophene)

We present nanoscale spatial extent of photogenerated polarons in a conjugated polymer, regioregular poly(3-octylthiophene). Light-induced electron-nuclear double-resonance (LENDOR) signals are clearly observed for the excitation around 1.8 eV due to the highly efficient photoinduced electron transfer in the polymer/fullerene composite. Broad LENDOR shifts directly reflect the spin density distribution of the polarons in the polymer. We determine its maximum shift using LENDOR-induced electron spin resonance, and evaluate the spatial extent of the polarons as ∼10 thiophene rings (∼4 nm).