14 November 2007 Enhanced electron injection and performance in organic light emitting devices by LiF doping
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Optimization of charge injection in the active emitting layer and balanced transport of carriers are important in realizing high efficiency and good reliability in organic light emitting devices (OLEDs). Electrical doping of such molecular materials with a view to enhancing their conductivity is an attractive route for enhancing the performance and versatility of these optoelectronic devices, in particular by enhancing carrier injection and lowering operating voltages. In the present study, we demonstrate efficient n-type doping of tris-(8-hydroxyquinoline) aluminum (Alq3) with the inorganic insulator lithium fluoride (LiF) by co-evaporation. The effect of dopant concentration on charge injection and carrier transport in this system is studied. We demonstrate that optimal doping not only leads to enhanced device currents and lower operating voltages, but also changes the charge transport from trap-limited to space-charge-limited transport. Using this scheme, we achieve efficient electron injection without using low work function cathodes. Finally, we employ the optimally-doped electron transport layers in OLED architectures to demonstrate devices with enhanced efficiency and lowered operating voltages.
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Kaushik Roy Choudhury, Kaushik Roy Choudhury, Jong-Hyuk Yoon, Jong-Hyuk Yoon, Franky So, Franky So, } "Enhanced electron injection and performance in organic light emitting devices by LiF doping", Proc. SPIE 6655, Organic Light Emitting Materials and Devices XI, 66551D (14 November 2007); doi: 10.1117/12.732537; https://doi.org/10.1117/12.732537

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