Singlet excitation energy transfer in tetracene-doped anthracene in thin film organic semiconductor

The electroluminescence (EL) spectra of pure and doped crystals appear to r esemble with the spectrum in thin film form. The EL spectra of tetracene, a nthracene and tetracene-doped anthracene in this film form have been report ed. But looking at the relative intensity of undoped anthracene and tetrace ne bands, it appears that the band of higher intensity of anthracene (host) has been quenched by the dopant and a large part of doped system lies in t he green region of the spectrum which is the characteristic emission of the dopant (guest) molecules, i.e., tetracene. The broadening of band for the doped molecule at 550 nm may be considered due to the energy transfer in th is system such that the doping quenches the blue emission of host molecule (anthracene) and replaces it with the green emission of the guest molecule (tetracene). The energy band diagram and a scheme for the excitonic reactio n kinetics, that agrees very well with experimental results have been const ructed. It is apparent from the comparison of brightness waves that the str ucture of the doped films resembles very much with that of the undoped tetr acene films.