title: Yield of singlet excitons in organic light-emitting devices: a double modulation photoluminescence-detected magnetic resonance study.
abstract: Double-modulation (DM) photoluminescence (PL) detected magnetic resonance (PLDMR) measurements on poly(2-methoxy-5-(2(')-ethyl)-hexoxy-1,4-phenylene vinylene) are described. In these measurements, the laser excitation power is modulated at 1<f(L)<100 kHz, and the spin-1/2 PLDMR of the PL response at f(L) is monitored by microwave modulation at f(M)<<f(L). The frequency response of the DM-PLDMR is inconsistent with the assumption that the PLDMR is due to delayed PL from nongeminate polaron recombination, which is the basis for previous predictions of the singlet-exciton (SE)-to-triplet exciton (TE) ratio in organic light-emitting devices. Rather, the frequency response is consistent with the assumption that the PLDMR is due to variations in the rate of quenching of SEs by TEs and polarons.
authors.affiliation: Ames Laboratory - USDOE and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA.
authors.forename: M-K
authors.initials: MK
authors.lastname: Lee
authors.forename: M
authors.initials: M
authors.lastname: Segal
authors.forename: Z G
authors.initials: ZG
authors.lastname: Soos
authors.forename: J
authors.initials: J
authors.lastname: Shinar
authors.forename: M A
authors.initials: MA
authors.lastname: Baldo