title: Spin-dependent recombination probed through the dielectric polarizability.
abstract: Despite residing in an energetically and structurally disordered landscape, the spin degree of freedom remains a robust quantity in organic semiconductor materials due to the weak coupling of spin and orbital states. This enforces spin-selectivity in recombination processes which plays a crucial role in optoelectronic devices, for example, in the spin-dependent recombination of weakly bound electron-hole pairs, or charge-transfer states, which form in a photovoltaic blend. Here, we implement a detection scheme to probe the spin-selective recombination of these states through changes in their dielectric polarizability under magnetic resonance. Using this technique, we access a regime in which the usual mixing of spin-singlet and spin-triplet states due to hyperfine fields is suppressed by microwave driving. We present a quantitative model for this behaviour which allows us to estimate the spin-dependent recombination rate, and draw parallels with the Majorana-Brossel resonances observed in atomic physics experiments.
authors.affiliation: Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK.
authors.forename: Sam L
authors.initials: SL
authors.lastname: Bayliss
authors.affiliation: Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK.
authors.forename: Neil C
authors.initials: NC
authors.lastname: Greenham
authors.affiliation: Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK.
authors.forename: Richard H
authors.initials: RH
authors.lastname: Friend
authors.affiliation: LPS, Université Paris-Sud, CNRS, UMR 8502, F-91405 Orsay, France.
authors.forename: Hélène
authors.initials: H
authors.lastname: Bouchiat
authors.affiliation: Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK.|LPS, Université Paris-Sud, CNRS, UMR 8502, F-91405 Orsay, France.
authors.forename: Alexei D
authors.initials: AD
authors.lastname: Chepelianskii