Achievement of complete electromer emission in organic light-emitting diodes

Electromer is a unique excited-state species which can only be formed under electrical excitation. Currently, a clear understanding of electromer has not been realized yet. A big obstacle is that the electromer emission can hardly be separated from the emission of molecular excitons. Obtaining a complete electromer emission is essential for photophysical investigations of this kind of excited-state species and is useful for its potential application in optoelectronic logic gates. We report that a complete electromer emission can be achieved by introduction of a weak-fluorescence layer in organic light-emitting diodes, which will quench the molecular excitons produced in the adjacent emissive layer but leave the electromers undisturbed. In addition, a possible mechanism for the electromer formation is proposed based on the analysis of the single crystal structure of the compound 9,9-bis[4-(di-p-tolyl)aminophenyl]-2,7-bis(9-carbazolyl)fluorene which can produce electromers.