Low voltage organic light emitting diode using p–i–n structure

Efficient n-type doping has been achieved by doping Liq in electron transport material Alq3. Detailed investigation of current density–voltage characteristics of electron only devices with different doping concentrations of Liq in Alq3 has been performed. An increase in current density by two orders of magnitude has been achieved with 33 wt% of Liq doped in Alq3. Organic light emitting diode with p–i–n structure was fabricated using F4-TCNQ doped α-NPD as hole transport layer, Ir(ppy)3 doped CBP as emitting layer and 33 wt% Liq doped Alq3 as electron transport layer. Comparison of OLEDs fabricated using undoped Alq3 and 33 wt% Liq doped Alq3 as electron transport layer shows reduction in turn on voltage from 5 to 2.5 V and enhancement of power efficiency from 5.8 to 10.6 lm/W at 5 V.