The dynamics of populating and depoulating of a phosphorescent triplet state as studied by microwave induced delayed phosphorescence

Visualizing the radical-pair mechanism of molecular magnetic field effects by magnetic resonance induced electrofluorescence to electrophosphorescence interconversion

“…the individual carrier spins 43 . This phosphorescencedetected magnetic resonance should not be confused with the spin-1 detection of the triplet exciton resonance, which has been reported previously in molecular emitters but probes spin conversion within the triplet manifold rather than singlet-triplet transitions [24][25] . We also note that in our early measurements of magnetoEL on PhLPPP we were not able to resolve these very subtle spectral differences due to limitations in sensitivity 28 .…”

“…However, device current -like the reaction yield in spin chemistry -is ultimately a secondary integral quantity which reports on changes in spin-pair permutation symmetry without directly probing singlet or triplet pair population density. Magnetic resonance has, of course, been probed in organic molecules by monitoring the fluorescence of singlets [21][22][23] and the phosphorescence of triplet excited states [24][25][26] . However, there are no reports of simultaneous probing of the two radiative recombination channels which would be required to monitor interconversion between spin species.…”

Coherent Spin Manipulation in Molecular Semiconductors: Getting a Handle on Organic Spintronics

“…The technique is particularly suited to investigations involving materials with weak spin-orbit coupling, where the differences in lifetime between the three excited-state triplet sublevels give rise to a spin-dependent buildup of macroscopic polarization. [43][44][45][46][47][48] In its simplest application, the attenuation of a microwave field is measured by the absorption of radiation resulting from transitions between an electron spin being parallel or antiparallel to an external magnetic field. This technique has been important in studying the effect of doping on the generation of carriers in conducting polymers, [49][50][51][52][53][54][55][56][57][58][59][60] but has also been widely used to reveal photogeneration of charge carriers in conjugated semiconducting materials.…”

“…[19] In this context it is worth noting the wealth of literature from the early days of molecular magnetic resonance spectroscopy, which can readily be related to present-day problems in organic electronics. Examples include the demonstration of a variety of coherent phosphorescence (triplet exciton)-detected magnetic resonance effects, [43][44][45][46][47]114] such as coherent spin polarization beating. [159] The contribution of hyperfine fields to charge-carrier dynamics in organic semiconductors has long been considered to be important.…”

Kinetics of the triplet state of 2,3-dichloroquinoxaline from microwave-induced phosphorescence transients

“…the decay constants of the individual triplet sublevels, the relative radiative rate constants, the relative populating rate constants, and spin-lattice relaxation rate constants. Dynamic information of a quantitative nature may be obtained from experiments such as microwave-induced delayed phosphorescence [8,9], optical detection of adiabatic inversion [10,11] and, more recently, the analysis of phosphorescence transients which follow a saturating fast-passage [12].…”