Materials and device structures for high performance poly OLEDs on flexible plastic substrates

Organic polymer light-emitting devices (Poly OLEDs) with the bi-layer thin film structures have been fabricated on both glass and flexible plastic substrates. The structural, optical, and electrical properties of each organic polymer layer have been optimized for the Poly OLED optimum electrical performances. The spin coating technique was used to fabricate our devices. An alternating co-polymer of poly (9, 9 ' -dihexyl fluorene-2, 7-diyl) and poly (benzothiadiazole 2, 5-diyl) (PHF-BTD), and poly (9-hexyl carbazole-3, 6-diyl) (PC6) have been used as light emitting and hole transporting polymer, respectively. The combination of the optical and cyclic voltammetry (CV) analysis has been used to develop the band diagram for our Poly OLEDs. For our polymers, the oxidation / reduction processes are well defined and clearly observed in the CV spectra. This allows a direct comparison of the polymers band gaps determined by both the optical and electrical methods. The photoluminescence and electroluminescence emission peaks are both located around 570 nm, and maximum brightness up to 2000 cd/m(2) was obtained. Turn-on voltages of similar to 16 and similar to 20 V, acceptable emission efficiencies of similar to5.5 and similar to4.2 cd/A, good power efficiencies of similar to0.9 and 0.6 lm/W, and acceptable external quantum efficiencies of 1.8 and 1.6 % have been obtained for OLEDs fabricated on both glass and plastic substrates, respectively.