Fig. 1. (a) Left, chemical structure of PBDB-T and, right, a schematic representing the plasmonic hybrid system of a PBDB-T matrix and P3HT-Au NPs. 2D GI-XRD patterns of (b) a neat PBDB-T film and hybrid films with PBDB-T/P3HT-Au NPs mass ratios of (c) 3:1 and (d) 1:1. (e) qz (out-of-plane) and qxy (in-plane) scans obtained from the GI-XRD patterns. (f) Left, absorption and, right, PL spectra of the neat film (dotted) and the hybrid films with the ratios of 3:1 (dotted–dashed) and 1:1 (solid). The samples were excited at 520 nm to obtain the PL spectra.

Fig. 2. Peak-normalized absorption spectra of a neat PBDB-T film (dotted) and hybrid films with PBDB-T/P3HT-Au NPs mass ratios of 3:1 (dotted–dashed) and 1:1 (solid).

Fig. 3. PL enhancement factor of the hybrid film with the 1:1 ratio compared to the neat PBDB-T film: (a) the experimental value and (b) the simulation value obtained by a finite-difference time-domain (FDTD) method.

Fig. 4. Transient absorption (TA) spectra of (a) a neat PBDB-T film and hybrid films with PBDB-T/P3HT-Au NPs mass ratios of (b) 3:1 and (c) 1:1.

Fig. 5. TAS of the neat film (solid) and a blend film of PBDB-T/PC71BM (dotted). The samples were excited at 620 nm.

Fig. 6. Pump-intensity-dependent TA kinetics of the neat PBDB-T film pumped with 620 nm and probed at 1180 nm. Dotted lines are best-fitted curves to extract decay constants.

Fig. 7. (a) Transient-absorption (TA) spectra and (b) kinetics of the neat PBDB-T film and the hybrid films. The samples were excited at 520 nm of 1.6  μJ/cm2 and probed at 1180 nm for the singlet (S1)-exciton TA kinetics of the films. The schematic kinetic-diagrams representing the excited-state dynamics of the neat and the hybrid systems (bottom): i, the S1 relaxation process; ii, the formation of positive (P+) and negative polarons (P−); iii, the geminate recombination of S1-excitons to the ground state.

Fig. 8. Decay-associated difference spectra obtained from the TA data fitted globally to an exponential decay equation described in Eq. (1): (a) the neat film; (b) the hybrid film with the ratio of 3:1; (c) the hybrid film with the ratio of 1:1.

Fig. 9. Absorption spectra of the neat PBDB-T films.

Fig. 10. Decay-associated difference spectra obtained from the TA data of the neat films fitted globally to an exponential decay equation described in Eq. (1).

Fig. 11. (a), (b) Species-associated spectra and (c), (d) model population kinetics of the given species. (e), (f) The selective wavelengths kinetics of the TA data fitted globally to the nonlinear kinetic equations described in Eq. (3). [(a), (c), and (e) the neat film; (b), (d), and (f) the hybrid film with the 1:1 ratio.]

Fig. 12. Schematic representing the excited-state dynamics of the neat PBDB-T system (left) and schematic representing the changed excited-state dynamics of the hybrid system by the hot-electron injection (HEI) from the P3HT-coated Au NPs to the PBDB-T matrix (right; the HEI-induced PL enhancement mechanism and the suppression of back charge-transfer from PBDB-T to the Au NPs by the P3HT chains tethered to the Au NPs).

Fig. 13. TA spectra of the neat P3HT and P3HT-Au NPs films. The samples were excited at 520 nm.

Fig. 14. PL spectra of the neat PBDB-T (solid) and blend P3HT/PBDB-T films. The samples were excited at 520 nm.