The Role of the Initial Charge Separation in the Geminate Pair Recombination in Disordered Molecular Systems

• Published in: Molecular crystals and liquid crystals science and technology. Section A, Molecular crystals and liquid crystals Vol. 355; no. 1; pp. 127 - 148
• Main Authors: Abramavicius, Darius, Gulbinas, Vidmantas, Valkunas, Leonas
• Format: Journal Article
• Language: English
• Published: Taylor & Francis Group 01.01.2001
• Subjects: geminate recombination; Monte-Carlo simulation; photogeneration; sensitisation
• ISSN: 1058-725X
• DOI: 10.1080/10587250108023658

Geminate charge pair recombination in sensitised photoconducting polymers was investigated by means of Monte-Carlo simulations. It was found that the initial charge separation distance and the hole recombination rate in the charge transfer (CT) complex, formed between a matrix molecule and a sensitiser, are the main parameters determining the initial part of the recombination kinetics. By comparing the simulation results to the experimentally observed kinetics of sensitised carbazolyl-containing polymers, it has been concluded that part of the charge pairs remain at the CT complexes and recombine exponentially. For the rest, the holes are separated from the CT complexes and cause much slower nonexponential decay. The time scale for the hole hopping steps was estimated to be of the order of 10÷50ps. A model of dynamical scattering of the mobile charges by sensitiser molecules at the initial stage of charge separation is suggested to explain faster recombination at high concentration of the sensitiser.