Effect of Encapsulation Technology on Organic Light Emitting Diode Lifetime

A kind of green organic light-emitting diodes (OLED) was prepared via vacuum thermal evaporation, of which the multilayer structure was indium-tin oxide (ITO)/copper-phthalocyanine (CuPc) (200 angstrom)/N,N'-bis(1-naphthyl)-N, N'-diphenyl- 1,1'-biphenyl-4,4'-diamine (alpha-NPD) (600 angstrom)/N'-diphenyl-N,N'-tris(8-hydroxyquinoline) aluminium (Alq3) (400 angstrom):10-(2-benzothiazolyl)-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H,11H-(1)benzopyropyrano(6,7,8-i,j)quinolizin-11- one (C545T) (2%)/Alq3 (200 angstrom)/LiF (10 angstrom)/Al (1000 angstrom). And we used both traditional glass encapsulation and thin film encapsulation (TFE) technologies to protect the device, reducing impact of vapor and oxygen. Organic film offered an excellent surface morphology, while inorganic film was nearly a perfect barrier to vapor and oxygen. Both of them constituted the encapsulation unit of TFE. According to the results of acceleration life test, the operation lifetime of device using TFE was 22% less than that of device using traditional glass cap encapsulation. So, the technology of TFE should be optimized further, and the quality of TFE needs a great improvement. There is a long way to go and a lot of hard work before realizing flexible display with OLED, but the dream will be true one day. (C) 2012 The Japan Society of Applied Physics