藍色主-客發光體之開發與有機電激發光元件之應用

Abstract

本論文以藍光OLED主-客發光系統之開發為主題，並將其應用於白光OLED的製作與元件穩定性的改良。以下將分為四個研究主題各別簡介： (1) 淺藍光OLED： 利用雙胺基取代苯乙烯衍生物為藍色客發光體材料，p-bis(p-N,N-diphenyl-aminostyryl)benzene (DSA-Ph)，搭配上一高薄膜穩定性之藍色主發光體材料，2-methyl-9,10-di(2-naphthyl)anthracene (MADN)，元件之發光效率可達9.7 cd/A和功率為5.5 lm/W於20 mA/cm2電流密度和5.7 V操作電壓下，其色度座標為[0.16, 0.32]。此淺藍光OLED主-客發光系統，其操作穩定性可達46,000小時於100 cd/m2亮度操作下。 (2) 深藍光OLED： 透過分子設計與合成，一系列不對稱性之單胺基取代苯乙烯分子，其放射波長可為深藍色客發光體所需之416~450 nm。當摻雜於主發光體材料MADN中，並以一複合式電洞傳輸層為元件架構下，元件發光效率可達5.4 cd/A和外部量子效率達5.1% 於20 mA/cm2電流密度操作下，而其色度座標為[0.14, 0.13]。此深藍光OLED主-客發光系統，其操作穩定性可達10,000小時於100 cd/m2亮度操作下。 (3) 白光OLED： 藉由一黃色客發光體摻雜於電洞傳輸層(NPB)中，2,8-di(t-butyl)-5,11-di[4-(t-butyl)phenyl]-6,12-diphenylnaphthacene (TBRb)，並將其導入於淺藍光OLED元件中(DSA-Ph@MADN)，可得到一雙波段白光OLED其發光效率為9.8 cd/A和功率為3.9 lm/W於20 mA/cm2電流密度和7.9 V操作電壓下，其色度座標為[0.31, 0.40]。當透過彩色濾光片後，其NTSC% 比率僅有58.7%。為了改善NTSC% 比率，將一綠和紅光OLED導入深藍光OLED元件中(2BpSA-Biph@□-MADN)，可得到一三波段白光OLED其發光效率為5.2 cd/A和功率為3.0 lm/W於20 mA/cm2電流密度和6.4 V操作電壓下，其色度座標為[0.31, 0.33]，並有效提高NTSC% 比率達68.1%。 (4) 元件穩定性： 利用DSA-Ph分子之好的電洞傳輸速率與特有之電洞捕捉能力，將其分別摻雜於C-545T綠光OLED元件中之電洞傳輸層、電子傳輸層和發光層中。相較於未摻雜時，其元件穩定性可分別被提升1.3、1.8和2.6倍，且元件操作穩定性可達16,000小時於100 cd/m2亮度操作下。

In this thesis, development of blue-doped organic light-emitting device (OLED) is the major subject, which has been applied in the fabrication of white OLED as well as improvement of the device stability. The study is divided into four sub topics as following: (1) Light-blue OLED: A highly efficient and stable blue OLED based on a distyrylamine (DSA) dopant, p-bis(p-N,N-diphenyl-aminostyryl)benzene (DSA-Ph) in a morphologically stable blue host material, 2-methyl-9,10-di(2-naphthyl)- anthracene (MADN) was demonstrated, which achieved an EL efficiency of 9.7 cd/A and 5.5 lm/W at 20 mA/cm2 and 5.7 V with a Commission Internationale d’Eclairage coordinates (CIEx,y) of [0.16, 0.32]. The light blue-doped device achieved a half-decay lifetime (t1/2) of 46 000 h at an initial brightness of 100 cd/m2. (2) Deep-blue OLED: New deep blue dopants based on unsymmetrical mono(styryl)amine derivatives were designed and synthesized, which provided us with the basic structure for color tuning within the spectral region between 416~450 nm. When doped in MADN host and incorporated a composite hole transport layer (c-HTL) as OLED, the device achieved an EL efficiency of 5.4 cd/A with a CIEx,y of [0.14, 0.13] and an external quantum efficiency of 5.1% at 20 mA/cm2. The deep blue-doped device achieved a half-decay lifetime (t1/2) of 10 000 h at an initial brightness of 100 cd/m2. (3) White OLED: When incorporating the 2,8-di(t-butyl)-5,11-di[4-(t-butyl)-phenyl]- 6,12-diphenylnaphthacene (TBRb) doped NPB as the yellow emitter into the two-element white OLED based on light-blue emitter (DSA-Ph@MADN), the device achieved an EL efficiency of 9.8 cd/A and 3.9 lm/W at 20 mA/cm2 and 7.9 V with a CIEx,y of [0.31, 0.40]. The NTSC ratio passed through the color filter is 58.7%. In order to improve the NTSC ratio, three-element white OLED was fabricated, which consisted of green, red and deep-blue emitter (2BpSA-Biph@□-MADN). The device achieved an EL efficiency of 5.2 cd/A and 3.0 lm/W at 20 mA/cm2 and 6.4 V with a CIEx,y of [0.31, 0.33]. The NTSC ratio was improved by 10% to 68.1%. (4) Device stability: The stability of C-545T doped green OLED has been improved by doping DSA-Ph in hole-transporting, electron-transporting or emitter layer. Compared with the undoped device, the stability increased by a factor of 1.3、1.8 or 2.6, respectively and the half-decay lifetime (t1/2) of 16 000 h at an initial brightness of 100 cd/m2 was achieved.