ELECTRONIC-ENERGY TRANSFER IN THE CHARGE-TRANSFER CRYSTAL OF 2,3-DIMETHYLNAPHTHALENE-TETRACYANOBENZENE

Optical, spectroscopic and kinetic studies of mixed-stack charge-trans fer crystals of 2,3-dimethylnaphthalene with tetracyanobenzene (DMN-TC NB), undoped and doped with anthracene (concentrations 10(-5)-2 x 10(- 3) M/M), were performed between 5 and 300 K. The kinetic analysis of f luorescence and delayed fluorescence confirmed that excitons are self- trapped at low temperatures and they become mobile at higher temperatu res. The obtained activation energies of mobility of singlet and tripl et excitons are (380 +/- 50) and (165 +/- 30)cm(-1), respectively. Tri plet exciton motion (50-80 K range) is well described by the one-dimen sional hopping model. Above 80 K, the intersystem crossing transition, T-1 --> S-1, with the activation energy of (1450 +/- 100)cm(-1), beco mes an efficient deactivation channel for triplet excitons. The experi ments point to a possibility of structural disorder in DMN-TCNB crysta ls.