Figure 1

UV-Vis absorption spectra of RC diluted in solvents of increasing polarity: $o$-xylene, chloroform, and $o$-DCB. F8BT and TFB absorption spectra in dilute $o$-xylene solutions are also shown. The chemical structure of RC is shown on top of the figure.Reuse & Permissions

Figure 2

PL spectra of diluted solutions of (a) F8BT and (b) RC in solvents with increasing polarity, cyclohexane (solid line), $o$-xylene (dot line), chloroform (empty circles), $o$-DCB (filled circles). Excitation at 470 nm.Reuse & Permissions

Figure 3

The solvatochromic plot—the Stoke shift of the RC in different solvents with varying solvent parameter. The slope of the plot indicates the degree of intramolecular charge transfer in the excited state.Reuse & Permissions

Figure 4

Femtosecond to picosecond transient-absorption spectra of (a) F8BT in $o$-xylene solution and RC in (b) $o$-xylene, (c) chloroform, and (d) $o$-DCB solutions. Excitation at 490 nm.Reuse & Permissions

Figure 5

Normalized transient-absorption kinetics of RC (a) $o$-xylene, (b) chloroform, and (c) $o$-DCB solutions at 560 nm, 600 nm, and 650 nm, respectively, in a time window between 1 ns and $100\mu \text{s}$. The TA kinetics have been compared with the time-resolved fluorescence lifetime taken from the same solutions at the peak of the PL spectra (filled circles). The experimental data have been fitted (solid line) by a monoexponential function.Reuse & Permissions

Figure 6

(a) Time-resolved PL decays transients of $o$-DCB diluted solution traced at different spectral positions. Decays measured at room temperature. The instrument response is also shown. (b) Temperature-dependent PL spectra of RC in $o$-DCB diluted solution, normalized at 650 nm. The PL spectrum of F8BT $o$-DCB diluted solution is also shown. (c) Time-resolved PL decay transients at different temperatures traced at 550 nm of the same solution. The time-resolved PL decay of F8BT $o$-DCB solution and the instrument response are also shown. Excitation at 470 nm. The inset shows the PL intensity dependence on temperature for the short-wavelength part of the spectrum of RC $o$-DCB solution, obtained by integrating the decay traces between 10 and 40 ns. The straight line corresponds to a Boltzmann-type fit.Reuse & Permissions

Figure 7

(a) Charge-transfer model rationalized by the rate Eqs. (2) and (3). (b) The spectral profiles of the locally excited (LE) and the CT state of the random copolymer in $o$-DCB solution obtained from globally fitting the transient-absorption data. (c) Population dynamics of the LE and the CT state of the random copolymer in $o$-DCB solution obtained from a global fit of the transient-absorption data set.Reuse & Permissions