The
single-chain conformations and aggregated structures
of conjugated
polymers in precursor solutions affect the morphology of films and
their photoelectric properties. Dynamic/static light scattering, small-angle
neutron scattering, high-resolution transmission electron microscopy,
and selected area electron diffraction were employed to elucidate
the single-chain conformations and aggregated structures of efficient
donor polymers (PBDT-TTz and D18-Cl) in chloroform (CF, nonaromatic
solvent) and chlorobenzene (CB, aromatic solvent) for a range of concentrations
(0.03–5.0 mg/mL). D18-Cl presented a more rigid and extended
chain conformation in dilute CF solution. However, the relatively
flexible PBDT-TTz easily formed π–π interaction
with the aromatic CB molecules, thereby extending the main chain’s
conjugation length. Regulation of the extended single-chain conformation
in dilute solution resulted in the formation of a compact, ordered
aggregated structure at increased concentrations. In the liquid–solid
cross-phase transfer process, the ordered structures in the precursor
solution were effectively inherited by the subsequent films. From
dilute to concentrated solutions, the multistage self-assembled structures
of conjugated polymers directly affected their solid-state packing
and photoelectric properties of the resulting films. Through the regulation
of the ordered aggregation in their precursor solution, the hole mobilities
of PBDT-TTz and D18-Cl were increased by nearly an order of magnitude,
and the power conversion efficiency of the solar cells was enhanced
by 28.8%.