Saturation of the ODMR effect on singlet exciton induced emission in molecular crystals: Application to crystalline tetracene

Geminate and Nongeminate Recombination of Triplet Excitons Formed by Singlet Fission

“…A material satisfying the energetic requirements for efficient singlet fission is tetracene, in which the singlet and triplet-pair states are nearly degenerate, permitting photoluminescence to be used as the experimental observable [14][15][16][17][18][19]. However, since tetracene is difficult to process from solution, it has limited practical application.…”

“…is the triplet spin operator, and D and E reflect the magnitude of this dipole-dipole interaction between the electron and hole. Frankevich et al have demonstrated ODMR as an elegant tool to detect the spin-correlated, geminate, triplet pairs formed through the fission process in crystalline tetracene [29], and a theoretical treatment has been advanced by others, highlighting the role of molecular packing [16][17][18]. ODMR has also been applied to the more common scenario of nongeminate triplet-triplet annihilation in which two triplets recombine after a bimolecular encounter [30][31][32][33].…”

Radio-wave Effect on Singlet Fission in Polycrystalline Tetracene near Zero Magnetic Field

“…The TT pair either fuses into the S 1 spin selectively from the 1 TT state or dissociates into two Ts. Therefore, the dynamics of the TT pair, which is a critical factor affecting SF efficiency, has been studied using various techniques such as transient fluorescence spectroscopy, − magnetic field effects, − ,− electron spin resonance (ESR), − and optically detected magnetic resonance (ODMR). − Recently, using broadband ODMR measurements near zero field at 4 K, researchers measured the fine structure of the TT pair due to the ZFS interaction in a crystalline sample of 5,12-bis­[(triisopropylsilyl)­ethynyl]­tetracene (TIPS-Tc) to identify the sites of TT pairs in molecular crystals . In the present study, to demonstrate that the ODMR measurements near zero field are also useful for investigating the dynamics of the TT pair, we experimentally and theoretically investigated the effects of the magnetic field of radio frequency (RF) waves on the SF in polycrystalline Tc powder at room temperature using a parallel configuration of B 0 and RF fields ( B 1 ).…”