Light-emitting diodes based on an alternating copolymer containing triphenylamine and phenylene units (TPA-PPA) were prepared, and electrically and optically characterized. The diode with a structure of indium tin oxide/TPA-PPV/Al exhibited a “current anomaly” phenomenon. We demonstrated that the “current anomaly” is caused by a reverse internal electric field owing to the reabsorption of electroluminescent light rather than the changes in the aluminum-doping concentration during operation.

• Received 9 May 2001

DOI:https://doi.org/10.1103/PhysRevB.65.115211