Extended Data Fig. 2: Probe-wavelength-resolved resonant-IVS studies on non-fullerene acceptor (NFA) molecules in chloroform solution.
From: Decoupling excitons from high-frequency vibrations in organic molecules
Wavelength-resolved impulsive Raman map of a ITIC, b IO-4Cl, c o-IDTBR, d Y5, e Y6, f Y7. Transient absorption spectra at 1-2 picosecond are plotted in the right inset of every panel. We note that while the NFAs have a donor-acceptor structural motif, due to coplanar geometry and strong electronic conjugation through the fused rings, the HOMO and LUMO strongly overlap in space so that the dipole oscillator strength of the lowest energy transition in these materials is very high, as required for their use in photovoltaics (see the frontier MOs in Supplementary Information section 10). We also note that in many of these molecules the exciton is delocalised across a large spatial extent (greater than for the APDC-DTPA and TTM-3PCz molecules), but that this overall delocalisation does not suppress coupling to high-frequency modes significantly (Supplementary Information section 21) nor reduced resultant non-radiative recombination rate (Fig. 3c).
