Alternating current light-emitting diodes and their transient characteristics: Response time and carrier transport

We report the fabrication and characterization of alternating current light-emitting diodes (LEDs) with quinquethiophene as the emitting material. We have obtained equal electroluminescence intensity in both bias sections. From the frequency response of the LEDs, we have estimated the device response times and compared them with the response times obtained from the transient response of de LEDs. Langmuir-Blodgett film deposition technique has been employed to control the thickness of the emitting layer on the molecular scale. We have shown that the response times originate from the accumulation rather than the transit of charge carriers. We have compared the photo- and electroluminescence spectra of QT LEDs.