Highly efficient non-doped blue organic electroluminescent devices based on BCzVB
Efficient non-doped blue organic light-emitting device with a structure of ITO/MoO3/TAPC(1,1-bis((di-4-tolylamino)phenyl)cyclohexane,50 nm)/BCzVB(1,4-bis[2-(3-N-ethylcarbazoryl)vinyl]benzene,x nm)/CBP(4,4'-N,N'-dicarbazole-biphyenyl,20 nm)/BCzVB(x nm)/TPBi(1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene,20 nm)/LiF(1.5 nm)/Al were reported,in which two ultrathin layers of BCzVB as blue emitters were located at both the sides of ambipolar material CBP.When the thickness of BCzVB is 0.3 nm,the maximum luminance and external quantum efficiency are 12 800 cd/cm2 and 2.1%(current efficiency is 2.8 cd/A),respectively,and CIE-1931 coordinate is(0.15,0.17).The de-vice performance is further improved by optimizing the thickness of the hole injection layer MoO3.The maximum luminance and external quantum efficiency reach 14 200 cd/cm2 and 4.2%(5.66 cd/A),respec-tively,which is so far the highest efficiency for BCzVB based blue OLED reported in the literature.