Heterofission in pentacene‐doped tetracene single crystals

Abstract

Abstract The magnetic field and the temperature dependence of both guest and host fluorescence in penta‐eene‐doped tetracene single crystals is studied. From an analysis of the experimental results it is concluded that pentacene enters substitutionally into the host lattice sites and that thermally activated heterofission is site‐dependent with activation energies ≈︁ (0.13 ± 0.01) e V and ≦ 0.06 eV. From a kinetic fit to the temperature dependence of the green and red fluorescence, a thermally activated host singlet exciton diffusion coefficient ≈︁ 2 × 10 −2 cm 2 /s is inferred; its activation energy is estimated to be (0.018 ± 0.001) eV. The heterofission rate of ≈︁(4.7 ± 0.5) × l0 −10 cm 3 s −1 is determined and location of the pentacene triplet level is found to be at (0.86 ± 0.03) eV.