The electronic interaction among the ion-pair can strongly modulate excited state decay dynamics of the individual ions. Fig. (a) represents the diagonal cut of the 2D spectrum at T = 30 fs. As discussed earlier, the two features at ω t = 13000 cm -1 and 12380 cm -1 corresponds to F 4 TCNQ anion and P2 band of the polymer, respectively. The F 4 TCNQ anion has been shown to have a decay time constant of 200 fs via non radiative relaxation through a conical intersection while in the gas phase. Here, in the precursor solution mixture, the F 4 TCNQ anion shows a biexponential decay with the time constants: ∼30 and ∼200 fs, as shown in Fig. . This change in the excited state dynamics signifies the possible existence of heterogeneous interactions in solution. The F 4 TCNQ anion population that decays within ∼30 fs time constant represents a strong perturbation via electronic interaction with the polymer backbone, which constitutes the major population (70%). In our earlier work on F 4 TCNQ doped PBTTT, we showed how a new conical interaction pathway can modulate the excited state lifetimes of F 4 TCNQ anions. A minor population (30%) decays via ∼200 fs time constant (similar to gas phase decay constant 33 ) highlighting that this population does not get perturbed by the strength of the interaction with the polymer backbone, and possibly reflects the poor interaction strength among the ion-pair.