Systematic Substituent Control in Blue Thermally Activated Delayed Fluorescence (TADF) Emitters: Unraveling the Role of Direct Intersystem Crossing between the Same Charge-Transfer States

被引:19
作者
Ryoo, Chi Hyun [1 ]
Han, Jongseok [2 ,3 ]
Yang, Jung-hoon [1 ]
Yang, Kwangmo [2 ]
Cho, Illhun [1 ,3 ]
Jung, Seyoung [1 ]
Kim, Sehun [3 ]
Jeong, Hyein [3 ]
Lee, Changhee [2 ,3 ]
Kwon, Ji Eon [1 ,4 ,5 ]
Serdiuk, Illia E. [6 ]
Park, Soo Young [1 ,4 ]
机构
[1] Seoul Natl Univ, Dept Mat Sci & Engn, Lab Supramol Optoelect Mat LSOM, 1 Gwanak Ro, Seoul 08826, South Korea
[2] Seoul Natl Univ, Interuniv Semicond Res Ctr ISRC, Dept Elect & Comp Engn, 1 Gwanak Ro, Seoul 151742, South Korea
[3] Samsung Display, 1 Samsung Ro, Yongin 17113, South Korea
[4] Seoul Natl Univ, Res Inst Adv Mat RIAM, 1 Gwanak Ro, Seoul 08826, South Korea
[5] Korea Inst Sci & Technol KIST, Funct Composite Mat Res Ctr, Jeonbuk 55324, South Korea
[6] Univ Gdansk, Fac Math Phys & Informat, Wita Stwosza 57, PL-80308 Gdansk, Poland
基金
新加坡国家研究基金会;
关键词
blue devices; organic light emitting diodes; photoluminescence; TADF emitters; thermally activated delayed fluorescence; LIGHT-EMITTING-DIODES; EFFICIENCY; DESIGN;
D O I
10.1002/adom.202201622
中图分类号
T [工业技术];
学科分类号
08 ;
摘要
A molecular structural approach is applied by introducing substituent groups (X) to explore the structure-property correlation of thermally activated delayed fluorescence (TADF) mechanism and develop blue TADF materials. D-A-X emitters show blue emissions from 446 to 487 nm and exhibit high rate constants of reverse intersystem crossing (k(rISC)) from 0.76 x 10(6) to 2.13 x 10(6) s(-1). Organic light emitting diodes (OLEDs) based on D-A-X emitters exhibit efficient external quantum efficiency from 17.2% to 23.9%. Furthermore, the theoretical analysis of spin-flip transitions between states of various nature reveals that the highest rISC rates can be achieved by the increase of charge-transfer (CT) strength and enhancement of direct transition between triplet ((CT)-C-3) and singlet ((CT)-C-1) charge transfer states. Rotational tolerance of dihedral angle, low energy gap, and low reorganization energy between the (CT)-C-3 and (CT)-C-1 states provides fast rISC even when triplet states of different (LE) nature have much higher energy not to enable the three-level interaction. By both experimental and theoretical methods, the investigations reveal that for the design of efficient TADF-OLED emitters, the enhancement of the (CT)-C-3-(CT)-C-1 transition is as much important as that of (LE)-L-3-(CT)-C-1.
引用
收藏
页数:13
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