Photoinduced Carrier Dynamics in Organic Bulk Heterojunctions Studied by Sub-Picosecond Optical Pump-THz Probe Time Domain Spectroscopy

摘要

The purpose of this work is to validate an analysis procedure proposed by Nienhuys and Sundstrom (1) for extracting transient complex conductivity from optical pump-THz probe time domain spectroscopy measurements and to use this method to investigate the photoinduced carrier dynamics in P3HT/PCBM blends. The conductivity artifacts predicted in reference (1) were verified in experiments on GaAs, well-known to obey the Drude model, and corrected by the appropriate time and frequency domain transformations (I). Unlike the case for GaAs, the complex conductivities of the P3HT/PCBM blends were described by the Drude-Smith model (2). A significant drop in conductivity in the first pico-second after carrier generation was found to be mainly due to the decrease in mobility associated with polaron formation.