Fluorescence‐Detected Low Field Resonances in T–T Annihilation in the A‐TCNB Single Crystal Lineshape and Dynamic Parameters

Abstract

An investigation is made of the line shape of the low field resonances observed in the dependence of the fluorescence of a single A-TCNB CT crystal on the external magnetic field. It is shown that the resonance is caused by avoided crossing of magnetic sublevels of it single T-exciton arising when the direction of the field is close to the axis of the fine interaction tensor. An analytic expression for the resonance line shape is obtained. The spin-lattice relaxation rate of T-excitons, tions, (ol = (5 + 2) x 107 5-1, are determined. 3~c n e p a~e a~a n b~o HccneHoBaHa #opMa JIHHMH H H~K O I I O J I~B O~O p e 3 o~a~c a B BBBHCH-t-l --(1.0 0.3) x lo7 s-l as well as the rate of jumps between the planes of fast exciton migra-MOCTM @IIoOpeCUeHUHll MOHOKpHCTaJIJIa H n 3 A-TU6 OT IIOCTORHHOI'O BHeIUHerO MarH&iTHOI' O IIOJIR. Pe3J' JIbTaTbI HHTepIIpeTHpOBaHhI B IIpeJUIOJIO?KeHHH, YTO @JIIoOpeC-KBa3HIIePeCeYeHHeM MarHHTHbIX IIOAYpOBHefi T-3IECHTOHOB IIpH HaIIpaBJleHMH I I 0 3 R 6JIH3KOM Ic OCH TeH3Opa TOHKOrO B3aHMOAefiCTBIU€. B PaMKaX pawee IIpe&JlOWeHHOfi UeiIuHH 06yCJIOBJIeHa TT-aHHmrHnRuet. n o~a 3 a~0 , YTO 3TOT pe30HaHc 06yCJIOBJIeH MoAenH TT-aHHHrmnHqm nonyseHa aHanklTmecHaR #opMyna ~IJIR (POPM~I JIHHHH p e a o~a~c a . OnpeaeneHa crcopomb CPP T-3ISCHTOHOB: t -l = (1.0 & 0,3) x lo7 s-l H CKOpOCT b IIpbImHOB Meway IIJIOCKOCTRMH 6bIcTpofi MHrpaUHH 3KCHTOHOB O1 = (5 f 2) X x 107 8-1.

Manifestation of T-exciton migration in the kinetics of singlet fission in organic semiconductors

“…This process is actively investigated for tens of years [1,2,4]. Intensive experimental investigations of fission kinetics inspired considerable theoretical studies of this process [1,2,[4][5][6][7][8][9][10][11].…”

Readout of Oriented Triplet Excitons in Linear Acenes via Room-Temperature Electrically Detected Magnetic Resonance

“…Based on these arguments, it appears that the dilution of Pc is required to detect isolated triplet spins. In fact, host–guest systems are commonly employed in EPR experiments in order to isolate single molecules in the solid state. ,− More specifically, neat polycrystalline Pc produces little to no resonant features in low temperature EPR experiments, but does reveal a distinct triplet spectrum when diluted in p -terphenyl. ,,− The two most commonly mentioned mechanisms in EPR literature that could cause peak attenuation are exciton delocalization and spin–lattice relaxation. − …”

“…Delocalization of excitonic species varies dramatically based on material, with some polymeric species exhibiting exciton delocalization upward of 50 nm, while most organics host an exciton on just one or two molecules. ,− Triplet exciton species tend to be more tightly bound and more localized than their singlet counterparts, and in the linear acenes tend to be constrained to one molecule at most. ,,,, In high concentration, neighboring molecules would tend to delocalize more, resulting in triplet transitions that are less constrained to the molecular axes and an overall reduction in the effective zero field splitting. On the other hand, spin–lattice relaxation effects are caused primarily via exciton hopping in the high concentration limit. , Triplet excitons are significantly less mobile than singlets in the linear acenes, but are still able to travel long distances due to considerable lifetimes. ,,− In the dilute regime, excitons would tend to be isolated and trapped, drastically reducing the spin–lattice relaxation and increasing the initial polarization caused by SF.…”

“…On the other hand, spin−lattice relaxation effects are caused primarily via exciton hopping in the high concentration limit. 97,98 Triplet excitons are significantly less mobile than singlets in the linear acenes, but are still able to travel long distances due to considerable lifetimes. 63,94,107−110 In the dilute regime, excitons would tend to be isolated and trapped, drastically reducing the spin−lattice relaxation and increasing the initial polarization caused by SF.…”