Application of wide-energy-gap material 3,4-di(9H-carbazol-9-yl) benzonitrile in organic light-emitting diodes

Abstract

A material with a wide energy gap, 3,4-di(9H-carbazol-9-yl)benzonitrile (2CzBN), was synthesized and applied in organic light-emitting diodes (OLEDs). Pure blue electroluminescence with a peak wavelength of 436 nm and Commission Internationale de l'Èclairage (CIE) coordinate of (0.160, 0.084) were obtained for an OLED containing 2CzBN as an emitter, although its external emission efficiency was limited to around 1% because of the lack of thermally activated delayed fluorescence (TADF) activity. In contrast, a highly efficient TADF-based OLED was obtained when 2CzBN was used as a host instead of an emitter by taking advantage of the high triplet energy (2.92 eV) and unexpected electron transport capability of 2CzBN.

Development of Pure Green Thermally Activated Delayed Fluorescence Material by Cyano Substitution

“…To demonstrate the potential of the proposed emitter, an OLED device was fabricated according to the following structure: indium tin oxide (ITO, 50 nm); N,N′′ ‐di(1‐naphthyl)‐ N,N′′ ‐diphenyl‐(1,1′′‐biphenyl)‐4,4′′‐diamine ( NPD , 40 nm); tris(4‐carbazolyl‐9‐ylphenyl)amine ( TCTA , 15 nm); 1,3‐bis( N ‐carbazolyl)benzene ( mCP , 15 nm); 0.5 wt% ν‐DABNA‐CN‐Me emitter; 99.5 wt% DOBNA‐Ph [ 12 ] (20 nm); 3,4‐di(9 H ‐carbazol‐9‐yl)benzonitrile ( 3,4‐2CzBN , [ 13 ] 10 nm); 2,7‐bis(2,2′‐bipyridine‐5‐yl)triphenylene ( BPy‐TP2 , [ 14 ] 20 nm); LiF (1 nm); and Al (100 nm). The EL characteristics, ionization potentials, and electron affinities of the various components of the device are shown in Figure .…”

Ultra‐Narrowband Blue Multi‐Resonance Thermally Activated Delayed Fluorescence Materials

“…To demonstrate the potential of the proposed emitters, devices with the following structure were fabricated: indium tin oxide (ITO, 50 nm); N,N ′‐di(1‐naphthyl)‐ N,N′ ‐diphenyl‐(1,1′‐biphenyl)‐4,4′‐diamine ( NPD , 40 nm); tris(4‐carbazolyl‐9‐ylphenyl)amine ( TCTA , 15 nm); 1,3‐bis( N ‐carbazolyl)benzene ( mCP , 15 nm); 1 wt% V‐DABNA or V‐DABNA‐F emitter and 99 wt% DOBNA‐Tol [ 3g ] (20 nm); 3,4‐di(9H‐carbazol‐9‐yl)benzonitrile ( 3,4‐2CzBN , [ 11a ] 10 nm); 2,7‐bis(2,2′‐bipyridine‐5‐yl)triphenylene ( BPy‐TP2 , [ 11b ] 20 nm); LiF (1 nm); and Al (100 nm). The electroluminescence characteristics, ionization potentials, and electron affinities of the fabricated devices are shown in Figure 3 .…”

Hypsochromic Shift of Multiple‐Resonance‐Induced Thermally Activated Delayed Fluorescence by Oxygen Atom Incorporation

“…To demonstrate the potential of the proposed emitter, devices with the following structure were fabricated: indium tin oxide (ITO, 50 nm); N , N′ ‐di(1‐naphthyl)‐ N , N′ ‐diphenyl‐(1,1′‐biphenyl)‐4,4′‐diamine ( NPD , 40 nm); tris(4‐carbazolyl‐9‐ylphenyl)amine ( TCTA , 15 nm); 1,3‐bis( N ‐carbazolyl)benzene ( mCP , 15 nm); 1 wt % ν‐DABNA‐O‐Me emitter and 99 wt % DOBNA‐Tol [8e, 16a] (20 nm); 3,4‐di(9H‐carbazol‐9‐yl)benzonitril ( 3,4‐2CzBN , [16b] 10 nm); 2,7‐bis(2,2′‐bipyridine‐5‐yl)triphenylene ( BPy‐TP2 , [16c] 20 nm); LiF (1 nm); and Al (100 nm). The EL characteristics, ionization potentials, and electron affinities of the device are shown in Figure 4.…”