Importance of poly(N-vinylcarbazole) dopant to poly(3-octylthiophene) electroluminescence

A new method is presented of enhancing the electroluminescence of short alkyl side chain poly(3-alkylthiophene) (P3AT) by adding poly(N-vinylcarbazole) (PVK) as a dopant in the emitting layer. The organic electroluminescent (EL) diode with one layer of poly(3-octylthiophene) (P3OT) and P3OT doped with various amounts of PVK (P3OT/PVK) as the EL-emitting layer sandwiched between indium/tin oxide and aluminum electrodes has been fabricated by spin-coating technique. The P3OT/PVK EL diode starts to emit red-orange light with an optimum molar ratio of P3OT to PVK at 5 V. Evidence suggests that the PVK dopant plays an important role in the P3OT electroluminescence. Such a molar ratio of P3OT to PVK is found to exist and acting mechanism of the dopant is investigated for enhancing the P3OT electroluminescence.