Ultrafast optical studies of ordered poly(3-thienylene-vinylene) films

Using femtosecond transient photomodulation, photoluminescence, and electro-absorption spectroscopies, we studied the ultrafast photoexcitation dynamics and nonlinear optical properties of ordered poly(thienylene-vinylene) (PTV), which belongs to a rare class of nonluminescent, nondegenerate-ground-state {π}-conjugated polymers. We show that the ordered PTV films contain abundant nanocrystalline domains that substantially influence the optical spectra as a result of aggregates formation. We demonstrate that the primary intrachain exciton (1¹Bᵤ) decays within {~}500 fs to the more stable ``dark'' exciton (20.16em0ex¹-0.16em0exAg), and the released energy results in both static strain and propagating strain wave that bounces back and forth in the polymer film.