Sensing electron transport in a blue-emitting copolymer by transient electroluminescence

A variation of the transient electroluminescence technique is introduced which allows us to selectively study the electron transport in a thin polymer layer. It relies on the formation of an insoluble interlayer from a formerly solvable polymer and enables probing of unipolar electron transport despite of injection barriers. It opens up possibilities to gain insight into the operation of light-emitting diodes. Applicability to a blue-emitting spirobifluorene-based copolymer is shown by comparison to time-of-flight results for electron and hole transport and evidence supplied for an intermixing of electron and hole dynamics through blocking of electrons at the polymer/anode interface. (C) 2007 American Institute of Physics.