We report wavelength and time-resolved photoluminescence studies of isolated extended (1-10 μm length) poly(3-hexylthiophene) (P3HT) nanofibers (xNFs) cast on glass from suspension. The PL spectra of xNFs show multiple vibronic replicas that appear to be associated with the existence of both H- and J-type aggregates. The PL spectra of xNFs made from regioregular (rr)- (93%) and highly regioregular (hrr)-P3HT (98%) both show similarities in PL spectra suggestive of common chain packing features, as well as subtle differences that can be attributed to higher long-range order in the hrr-xNFs. Specifically, PL spectral measurements on isolated xNFs made from highly regioregular (>98%) P3HT showed a red-shifted electronic origin (≈30 meV) and increased 0-0/0-1 PL intensity ratio for the J-type species, suggestive of enhanced structural coherence length and intrachain order.

Resonant inelastic light scattering experiments at nu = 1/3 reveal a novel splitting of the long-wavelength modes in the low energy spectrum of quasi-particle excitations in the charge degree of freedom. We find a single peak at small wave vectors that splits into two distinct modes at larger wave vectors. The evidence of well-defined dispersive behavior at small wave vectors indicates a coherence of the quantum fluid in the micron length scale. We evaluate interpretations of long-wavelength modes of the electron liquid.

Excitation modes in the range 2/5>or=nu>or=1/3 of the fractional quantum Hall regime are observed by resonant inelastic light scattering. Spectra of spin-reversed excitations suggest a structure of lowest spin-split Landau levels of composite fermions that is similar to that of electrons. Spin-flip energies determined from spectra reveal significant composite fermion interactions. The filling factor dependence of mode energies displays an abrupt change in the middle of the range when there is partial population of a composite fermion level.

We report on a remarkable size and internal structure dependence on time- and polarization-resolved photoluminescence (PL) from individual regioregular rrP3HT (poly-3-(hexylthiophine)) nanoparticles. For the smallest particles (∼34 nm) with relatively low crystallinity (40%), the time evolution of polarization contrast is nearly stationary; for intermediate-sized particles (∼ 65 nm), depolarization occurs on a 1–2 ns time scale. The largest and most crystalline particles studied (118 nm, 70%) show a PL depolarization on a time scale of <50 ps. In every time regime, we observe P3HT nanoparticle PL dynamics that are qualitatively different from those of extended films and single-polymer chains, highlighted by intriguing differences in power law dynamics in the PL intensity at long times. This work may support the hypothesis that hierarchical assemblies of conducting polymer nanoparticles could offer a route to higher efficiency in organic photovoltaic systems.