Fig. 1

Optical absorption and steady-state photoluminescence spectra in mixed solvents. a, b UV-vis-NIR absorption and steady-state photoluminescence spectra of D-PDPP4T-HD dissolved in chloroform:1,2,4-trichlorobenzene (CF:TCB) mixtures. The volume ratio (v/v) of CF and TCB is 1:0, 9:1, 2:1, 1:1, 1:2, 1:9, and 0:1, respectively. The polymer concentration is 0.4 μM in all cases. The gray area in a represents the absorption spectrum of the amorphous phase (α) in pure TCB at 100 °C (Supplementary Fig. 2). The characteristic peaks of the first (β₁) and the second (β₂) aggregated phases are indicated by purple and green frames, respectively. c The component contribution of each phase as a function of the TCB content, as inferred from the multivariate curve resolution alternating least squares deconvolution of the UV-vis-NIR spectra. Process I in c indicates the β₁ → α transformation when TCB content increases from 0 to 67%; process II indicates the α → β₂ transformation when the TCB content increases further from 67 to 100%. d Chemical structure of D-PDPP4T-HD. e Schematic illustration of polymorphism transitions of D-PDPP4T-HD