Charge Carrier Tunneling in the Light-Emitting Diodes of Poly(p-phenylene) Thin Film

Abstract

We have studied the temperature dependence of the current-voltage (I-V ) and the electroluminescence-voltage (EL-V ) characteristics in the blue light-emitting diodes of vacuumdeposited poly (p-phenylene) (PPP) thin lms in the temperature range between 14 and 290 K. The onset of the EL occurs at an electric eld of about 7107 V/m, independent of the thickness of the PPP layer. The I-V and EL-V dependences show very weak temperature dependences and t very well with the Fowler-Nordheim tunneling formula. The results suggest that charge carrier injection is a tunneling process through an energy barrier of about 0.60.8 eV in indium tin oxide (ITO)/PPP/Al devices.