TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preparation: No preparation method is given. Preferred Components: A distance between the lowest triplet state and the overlying singlet state is less than 2000 cm-1, preferably less than 300 cm-1. The lowest triplet state of (Q) has a zero-field splitting of sub-states I, II, III, where an energy gap between the sub states III and I is greater than 3 cm-1, preferably greater than 20 cm-1. (Q) has a radiative lifetime of the lowest triplet state of less than 100 mu s, preferably less than 5 mu s. (Q) is copper- (Cu(I)-) and/or silver- (Ag(I)-) central ion, comprises at least one polydentate ligand that binds to a central ion of the transition metal complex, and is a mononuclear, binuclear or multinuclear complex, in which the coordination to the metal center is three or four times. (Q) has metal-to-ligand charge transfer transitions, which have a highest occupied molecular orbital (HOMO)-share with a distinctive d-orbital character having d orbitals from central ions in dinuclear or polynuclear complexes, and a lowest unoccupied molecular orbital (LUMO) portion consisting of a pi orbital of a ligand, where the ligand is bound in dinuclear or polynuclear complexes at the central ions. The optoelectronic device comprises an emitter layer comprising (Q), where the concentration of (Q) in the emitter layer is 2-100 wt.%, preferably 20-80 wt.%. (Q) is selected according to the distance between the underlying singlet state and the lowest triplet state. Preferred Method: The selecting method further comprises determining the distance value, determining the energy gap between the sub states III and I of the lowest triplet state, implementing high-resolution spectroscopic measurements of emissions of 1.3-20 K, determining the value of the radiative emission decay of the triplet state, measuring the temperature dependence of the emission lifetime and emission quantum yield in a region of forming plateaus, and identifying (Q) whose distance value is less than 2000 cm-1. SPECIFIC COMPOUNDS - 30 Compounds (Q) are disclosed, e.g. copper complex of formulae (I)-(V).    EXAMPLE - No suitable example given.