Transient electroluminescence from PPV under strong voltage pulses

We have studied the transient electroluminescence (EL) from poly(phenylenevinylene), PPV, as a function of electric field under strong electric pulses up to fields of E ≈ 10⁹ V/m with emphasis on (a) the time delay, τ, between the electric pulse and the onset of the EL emission pulse and (b) the EL intensity as a function of the field. A monotonic decrease of τ with increasing E is explained by an increase of the carriers mobility according to Frenkel-Poole model. The EL intensity at high fields is proportional to E³ suggesting that the contacts at the polymer-metal electrode interfaces are practically ohmic. We demonstrate significantly improved brightness, peak power and lifetimes for polymer-based light emitting diodes working under such a pulsed mode.