Electric field suppression of hopping charge recombination

Abstract

Charge recombination in a poly(para-phenylene vinylene)-fullerene derivative composite film studied by transient, nonresonant, hole-burning spectroscopy Field effects on the recombination of atomic ions studied at a storage ring electron cooler AIP Conf.The theory of hopping reactions between charged particles in high-mobility non-polar liquids is essentially extended to account for the electric field effect on a bulk electron-ion recombination. It turns out that the rate constant of the hopping recombination decreases with the electric field contrary to what was obtained for diffusional recombination. Such a difference may serve for experimental discrimination between hopping and diffusional reaction mechanisms. Their interrelation is traced within a more general Torrey's model of a solvated electron random walk with an arbitrary step length determined by the free electron diffusion. The coefficient of linear field dependence obtained for low fields in the contact approximation changes the sign in passing from a short mean step length ͑diffusional recombination͒ to a much larger mean step length ͑hopping recombination͒.

Geminate Recombination in the Presence of Scavengers: The New Vision of the Old Problem

“…Being an obvious alternative to diffusion mechanism, the hopping mechanism was first proposed in papers [36,37] to describe luminescence impurity quenching experiments in solid solutions. For liquid phase reaction it is developed in papers [38][39][40][41][42] and was first found experimentally in excess electron capture reactions in nonpolar liquids [43].…”

“…Stationary rate constant (41) is equal to the sum of diffusion rate constant k (38), hopping rate constant V/τ B [36][37][38][39][40][41][42] and the interference term appearing due to the intricate character of reactants approach. The presence of this term is a distinguishing feature of stationary rate constant (41) of the two-scale bulk reaction.…”

“…As in the previous subsection, the introduced parameter γ is the bulk reaction rate in τ B units. Using (41), it can be rewritten in our case of diffusion motion of acceptor as γ = β + ξ + 3ξβ, where…”

“…This model allows us to obtain exact kinetic equations for the general type of A and C reactants mobility and the Coulomb interaction in a geminate pair [35]. The most essential assumption of the model is that B particle of a geminate pair (excess electron) reacting with scavengers C moves by infinitely large jumps (the hopping mechanism [36][37][38][39][40][41][42]). The hopping mechanism has been used more than once to describe the scavenging of an excess electron moving by random walks in solutions [40][41][42][43][44].…”

“…The most essential assumption of the model is that B particle of a geminate pair (excess electron) reacting with scavengers C moves by infinitely large jumps (the hopping mechanism [36][37][38][39][40][41][42]). The hopping mechanism has been used more than once to describe the scavenging of an excess electron moving by random walks in solutions [40][41][42][43][44]. This assumption of the large jumps is justified by the well-known fact that mean free path of excess electrons is fairly large in some solvent of low polarity [23,43,45] (≈60-200Å).…”