Effective Charge Extraction in the Heterogeneous Interfaces with TiO2 Nanoparticles/Nanotubes and Conducting Polymers

The properties of interfaces between organic and inorganic materials in heterojunctions are relevant to a variety of electronic applications. The performances of such devices strongly depend on the kinetics of the charge transfer reactions and the thermodynamic properties (e.g., energetic difference at the junctions) at the heterogeneous interfaces. Heterogeneous interfaces can be controlled by modifying the interfacial properties to improve the photovoltaic performance. After electron injection into the conduction band (CB) from a dye excited by photon absorption, an electron relaxes to the lowest energy level of the CB and is subsequently trapped in the intra-band states. Trapping then increases the electron collection time through the TiO₂ particles. The photoinduced electrons in the trap states can recombine with dye cations or the cationic hole transporting material. These recombination reactions are rapid (the characteristic electron recombination time, t_rec, is short) if many trap states in the lower-lying quasi-Fermi level of the TiO₂ electrode exist. In this talk, I present how to control such recombination reactions in a molecular levels toward zero electron loss in organic based photocells.