Fluorescent electronic device containing a sensitiser and a fluorescent emitter, where the sensitiser is a phosphorescent compound and where at least one of the two following conditions or must be satisfied, where it is preferred if condition is satisfied: S 1 K FE − S 1 K S ≥ X S 1 max FE − S 1 max S ≥ Y where the following applies to the parameters used: X, Y are each -0.5 eV S 1 K is the energy of the first excited singlet state of the fluorescent emitter, which is determined from the edge of the first maximum on the side of the short wavelength of the standardised photoluminescence spectrum of the fluorescent emitter; S 1 K is the energy of the first excited state of the sensitiser, which is determined from the edge of the first maximum on the side of the short wavelength of the standardised photoluminescence spectrum of the sensitiser; S 1 max is the energy of the first excited singlet state of the fluorescent emitter, which is determined from the position of the first maximum at small wavelengths of the photoluminescence spectrum of the fluorescent emitter; S 1 max is the energy of the first excited state of the sensitiser, which is determined from the position of the first maximum at small wavelengths of the photoluminescence spectrum of the sensitiser; where the photoluminescence spectra of the sensitiser and of the fluorescent emitter are determined from solution at a concentration of 1 mg in 100 ml of toluene at room temperature, where the fluorescent emitter is a sterically shielded compound which has a shielding factor of greater than or equal to 0.5, preferably greater than or equal to 0.6 and particularly preferably greater than or equal to 0.65, where the shielding factor is determined by the method described in the description, where the sensitiser is a phosphorescent compound from the group of the organometallic complexes containing Cu, Ir, Pt, Rh, Ru, Os or Pd and preferably Ir and Pt, and where the fluorescent emitter is a purely organic compound without metals or metal ions which is selected either from the group of the condensed aromatic compounds having 6 to 60 aromatic ring atoms or from compounds having a heteroaromatic skeleton from the groups of the formulae to shown below, X, Y are each -0.5 eV S 1 K is the energy of the first excited singlet state of the fluorescent emitter, which is determined from the edge of the first maximum on the side of the short wavelength of the standardised photoluminescence spectrum of the fluorescent emitter; S 1 K is the energy of the first excited state of the sensitiser, which is determined from the edge of the first maximum on the side of the short wavelength of the standardised photoluminescence spectrum of the sensitiser; S 1 max is the energy of the first excited singlet state of the fluorescent emitter, which is determined from the position of the first maximum at small wavelengths of the photoluminescence spectrum of the fluorescent emitter; S 1 max is the energy of the first excited state of the sensitiser, which is determined from the position of the first maximum at small wavelengths of the photoluminescence spectrum of the sensitiser; where the photoluminescence spectra of the sensitiser and of the fluorescent emitter are determined from solution at a concentration of 1 mg in 100 ml of toluene at room temperature, where the fluorescent emitter is a sterically shielded compound which has a shielding factor of greater than or equal to 0.5, preferably greater than or equal to 0.6 and particularly preferably greater than or equal to 0.65, where the shielding factor is determined by the method described in the description, where the sensitiser is a phosphorescent compound from the group of the organometallic complexes containing Cu, Ir, Pt, Rh, Ru, Os or Pd and preferably Ir and Pt, and where the fluorescent emitter is a purely organic compound without metals or metal ions which is selected either from the group of the condensed aromatic compounds having 6 to 60 aromatic ring atoms or from compounds having a heteroaromatic skeleton from the groups of the formulae to shown below,