Design of new anchored p-dopants for high power efficiency OLEDs

Description/Abstract

Conductivity doping of charge transporting layers is increasingly becoming attractive for improving power efficiency in OLEDs. However, the number of organic molecular p-dopants is limited for instance the electron acceptor 2,3,5,6-tetrafluoro-7,7,8,8,-tetracyanoquinodimethane (F4-TCNQ) is the most utilized p-dopant. F4-TCNQ can dope most hole transporting materials (HTL), but it is very volatility, and has a low sticking coefficient thus difficult to deposit. Here we present the design of anchored molecular dopants based on the TCNQ core. We first review how the reduction potential of TCNQ core is affected by substitution with alkyl groups of different electronic properties. Electron donating groups have negative effect on the reduction potential of the acceptor. However, attaching electron withdrawing groups such as halogens counteracts the effect of electron donating groups. Using gas phase theoretical calculations we determined that trifluorinated TCNQ can be anchored through a -coupled alkyl chain to an inert molecular anchor without sacrificing the electron affinity.