TY - JOUR
T1 - Alternative p-doped hole transport material for low operating voltage and high efficiency organic light-emitting diodes
AU - Murawski, Caroline
AU - Fuchs, Cornelius
AU - Hofmann, Simone
AU - Leo, Karl
AU - Gather, Malte C.
N1 - This work received funding from the European Community Seventh Framework
Programme under Grant Agreement No. FP7 267995 (NUDEV) and from the European Social Fund and the free state of Saxony through the OrganoMechanics project.
PY - 2014/9/15
Y1 - 2014/9/15
N2 - We investigate the properties of N,N'-[(Diphenyl-N,N'-bis) 9,9,-dimethyl-fluoren-2-yl]-benzidine (BF-DPB) as hole transport material (HTL) in organic light-emitting diodes (OLEDs) and compare BF-DPB to the commonly used HTLs N,N,N',N'-tetrakis(4-methoxyphenyl)-benzidine (MeO-TPD), 2,2',7,7'-tetrakis(N,N'-di-p-methylphenylamino)-9,9'-spirobifluorene (Spiro-TTB), and N, N'-di(naphtalene-1-yl)-N,N'-diphenylbenzidine (NPB). The influence of 2,2'-(perfluoronaphthalene-2,6-diylidene)dimalononitrile (F6-TCNNQ p-dopant) concentration in BF-DPB on the operation voltage and efficiency of red and green phosphorescent OLEDs is studied; best results are achieved at 4 wt. % doping. Without any light extraction structure, BF-DPB based red (green) OLEDs achieve a luminous efficacy of 35.1 lm/W (74.0 lm/W) at 1000 cd/m(2) and reach a very high brightness of 10 000 cd/m(2) at a very low voltage of 3.2 V (3.1 V). We attribute this exceptionally low driving voltage to the high ionization potential of BF-DPB which enables more efficient hole injection from BF-DPB to the adjacent electron blocking layer. The high efficiency and low driving voltage lead to a significantly lower luminous efficacy roll-off compared to the other compounds and render BF-DPB an excellent HTL material for highly efficient OLEDs.
AB - We investigate the properties of N,N'-[(Diphenyl-N,N'-bis) 9,9,-dimethyl-fluoren-2-yl]-benzidine (BF-DPB) as hole transport material (HTL) in organic light-emitting diodes (OLEDs) and compare BF-DPB to the commonly used HTLs N,N,N',N'-tetrakis(4-methoxyphenyl)-benzidine (MeO-TPD), 2,2',7,7'-tetrakis(N,N'-di-p-methylphenylamino)-9,9'-spirobifluorene (Spiro-TTB), and N, N'-di(naphtalene-1-yl)-N,N'-diphenylbenzidine (NPB). The influence of 2,2'-(perfluoronaphthalene-2,6-diylidene)dimalononitrile (F6-TCNNQ p-dopant) concentration in BF-DPB on the operation voltage and efficiency of red and green phosphorescent OLEDs is studied; best results are achieved at 4 wt. % doping. Without any light extraction structure, BF-DPB based red (green) OLEDs achieve a luminous efficacy of 35.1 lm/W (74.0 lm/W) at 1000 cd/m(2) and reach a very high brightness of 10 000 cd/m(2) at a very low voltage of 3.2 V (3.1 V). We attribute this exceptionally low driving voltage to the high ionization potential of BF-DPB which enables more efficient hole injection from BF-DPB to the adjacent electron blocking layer. The high efficiency and low driving voltage lead to a significantly lower luminous efficacy roll-off compared to the other compounds and render BF-DPB an excellent HTL material for highly efficient OLEDs.
KW - Electroluminescent devices
KW - Roll-off
KW - Layers
KW - Dopants
U2 - 10.1063/1.4896127
DO - 10.1063/1.4896127
M3 - Article
SN - 0003-6951
VL - 105
JO - Applied Physics Letters
JF - Applied Physics Letters
IS - 11
M1 - 113303
ER -