Pure white organic light-emitting devices with excellent color stability using a non-doped 4-aryloxy-1,8-naphthalimide derivative

Pure white organic light emitting devices (OLEDs) with high color stability have been fabricated, using a 4-aryloxy-1,8-naphthalimide derivative FluONI as a non-doped blue emitting layer (EML) combined with orange emitting exciplex at the interface of electron donor/FluONI. Three kinds of hole transport materials consisting of amino groups with stepped highest occupied molecular orbital (HOMO) levels are introduced as electron donors for the modulations of exciplex emission band and hole injection barrier. As a result, pure white emission with a standard Commission Internationale de 1'Eclairage (CIE) coordinate of (0.33, 0.33) is achieved by adopting N,N′-diphenyl-N,N′-bis(1-naphthyl)-1,1′-biphenyl-4,4″-diamine as an electron donor with a relatively deep HOMO level and a 30 nm-thick EML. Meanwhile, excellent color stability is also observed with a slight CIE coordinates shift of (0.01, 0.01) at a luminance range from 100 to 4000 cd/m2. According to the systematic analyses on electroluminescence spectra, the pure white emission benefits from the broad emission bands of both FluONI and exciplex. The pure white emission with high color stability at different drive voltages are attributed to the sustainable equilibrium between FluONI intrinsic and exciplex emission. Our devices based on a single non-doped EML provide a simple way to realize color pure and stable white OLEDs.