Reliability Study of a Fluorescent Blue Organic Light-Emitting Device
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0965-S03-11
Reliability Study of a Fluorescent Blue Organic Light-Emitting Device Jiun-Haw Lee1,2, Yu-Hsuan Ho1, Tien-Chun Lin1, and Chia-Fang Wu1 1 Graduate Institute of Electro-Optical Engineering, National Taiwan Univ., 1, Sec. 4 Roosevelt Rd., Taipei, 10617, Taiwan 2 Department of Electrical Engineering, National Taiwan Univ., 1, Sec. 4, roosevelt Rd., Taipei, 10617, Taiwan
ABSTRACT In this paper, we measured and analyzed the operation lifetime of a high efficiency blue organic light-emitting device (OLED) which consists of N,N’ –diphenyl -N,N’-bis(1-napthyl) 1,1’-biphenyl-4,4’- diamine (NPB) as the hole-transport layer, 4,4'-bis[2-(4-(N,Ndiphenylamino)phenyl)vinyl]biphenyl (DPAVBi) doped in 9,10-bis(2’-naphthyl) anthracene (ADN) as the emitting layer, and bis(10-hydroxyben-zo[h]quinolinato)beryllium (Bebq2) as the electron-transport layer (ETL). Due to the high electron mobility of the ETL, the carrier balance is achieved and a blue OLED with a high external quantum efficiency of 8.32% is obtained. From accelerated lifetime test, the estimated half lifetime at an initial luminance of 1000 cd/m2 achieves 15611 hours in our device. For further investigating the lifetime mechanism in our blue OLED, we fit all the luminance versus time curves obtained under different driving condition. INTRODUCTION Organic light-emitting devices (OLEDs) have attracted much attention due to the advantages of fast response, light-weight, self-emitting, and wide view-angle [1,2]. To achieve white lighting or full color display, a blue OLED is essential and it is the bottleneck among the three primary colors due to the lower current efficiency and shorter lifetime, compared with red and green ones. There are two major material systems are used as the emitting layer (EML) for the blue OLED: (1) 4,4'-bis(2-(9-ethyl-9H-carbazol-3-yl)vinyl)biphenyl (BCzVBi) doped in the distyrylarylene (DSA) derivative matrix [3], and (2) 2,5,8,11-tetra(t-butyl)-perylene (TBP) doped in the diphenylanthracene derivatives 9,10-di(2-naphthyl)anthracene (ADN) matrix [4]. It is also reported that, with the blue dopant p-bis(p-N,N-diphenyl-aminostyryl)benzene (DSA-Ph) in the 2-methyl-9,10-di(2-napthyl)anthracene (MADN), a blue OLED achieved a high EL efficiency of 9.7 cd/A at 20 mA/cm2 and 5.7 V with CIEx,y (0.16, 0.32) and a half-decay lifetime of 46000 h with an initial brightness of 100 cd/m2 [5]. In our study, we use the ADN as the host material and 4,4'-bis[2-(4-(N,Ndiphenylamino)phenyl)vinyl]biphenyl (DPAVBi) as the dopant material in the emitting layer (EML) to achieve a high current efficiency. Besides, we used the bis(10-hydroxybenzo[h]quinolinato)beryllium (Bebq2) as the electron transport layer (ETL) material that exhibits the electron mobility of about one orders of magnitude higher than that of the typically used ETL material, tris-(8-hydroxyquinoline) aluminum (Alq3) [6]. Hence, the carrier balance condition is achieved which effectively reduces the driving voltage, increases the power efficiency, and elongate the operation lifetime. When measuri
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