Transient Spectroscopy of Frenkel and Charge Transfer Excitons inα-Sexithienyl Films

Abstract
Photoexcitations dynamics are investigated in α-sexithienyl nanocrystalline films using transient photomodulation in a spectral range from 0.4 to 2.5 eV and time domain from 200 fs to 50 ms. We identify intrachain and interchain excitations. The former are even parity excitons with ultrafast dynamics, whereas the latter are long-lived charge transfer excitons generated within 300 fs, which separate into uncorrelated polaron pairs in the submicrosecond time domain.