Abstract: The organic light-emitting diodes (OLEDs) have aroused intense interests from researchers owing to their prospects as the next generation display and lighting technologies. Traditional fluorescent materials cannot obtain satisfactory efficiency because they only realize singlet exciton luminescence. In recent years, it has been a great breakthrough that the electrofluorescence materials utilizing triplet ections energy for radiation in organic electronics have been developed. According to the transformation mechanism of triplet excitons to singlet exciton, fluorescent materials can be divided into three types including triplet-triplet annihilation, thermally activated delayed fluorescence, hybridized local and charge transfer excited state. This article specially focuses on small molecule based purely organic electrofluorescence emitters with amazing device performances. It begins with the general situation of organic electrofluorescence devices, then gives an overview of the fluorescence emitters with various electrofluorescence mechanisms, and finally provides specific molecular design strategies towards high efficiency devices.
1 Tang C W, VanSlyke S A. Organic electroluminenscentdiodes[J].Applied Physical Letters,1987,51:913. 2 Godumala M, Choi S, Ju M, et al. Thermally activated delayed fluorescence blue dopants and hosts: From the design strategy to organic light-emitting diode applications[J].Journal of Material Chemistry C,2016,4:11355. 3 Yang X L, Zhou G J, Wong W Y. Functionalization of phosphorescent emitters and their host materials by main-group elements for phosphorescent organic light-emitting devices[J].Chemical Society Reviews,2015,10:11735. 4 Su S J. A new generation of organic light-emitting materials and device[J].Chinese Science Bulletin,2016,61(32):3448(in Chinese). 苏仕健.新一代有机电致发光材料与器件[J].科学通报,2016,61(32):3448. 5 Im Y, Byun S Y, Kim J H, et al. Recent progress in high-efficiency blue-light-emitting materials for organic light-emitting diodes[J].Advanced Materials,2017,27:1603007. 6 Chen Y H, Lin C C, Huang M J, et al. Superior upconversion flurscence dopants for highly efficient deep-blue electroluminescent devices[J].Chemical Science,2016,7:4044. 7 Adachi C, Baldo M A, Forrest S R, et al. Nearly 100% internal phosphorescence efficiency in an organic light emitting device[J].Journal of Applied Physis,2001,90(10):5048. 8 Pu Y J, Nakata G, Satoh F, et al. Optimizing the charge balance of fluorescent organic light emitting devices to achieve high external quantum efficiency beyond the conventional upper limit[J].Advanced Materials,2012,24:1675. 9 Zhou J, Chen P, et al. Charge-transfer-featured materials-promising hosts for fabrication of efficient OLEDs through triplet harvesting via triplet fusion[J].Chemical Communications,2014,50:7586. 10 Lyu Y Y, Kawk J, Kwon O, et al. Silicon-cored anthracene derivatives as host materials for highly efficient blue organic light emitting devices[J].Advanced Materials,2008,20:2720. 11 Wang J, Lou X, Liu Y Q, et al. Controllable molecular configuration for significant improvement of blue OLEDs based on novel twisted anthracene derivatives[J].Dyes and Pigments,2015,118:137. 12 Chou P Y, Chou H H, Chen Y H, et al. Efficient delayed fluorescence via triplet-triplet annihilation for deep-blue electroluminescence[J].Chemical Communication,2014,50:6869. 13 Fukagawa H, Shimizu T, Ohbe N, et al. Anthracence derivatives as efficient emitting hosts for blue organic light-emitting diodes utilizing triplet-triplet anninilation[J].Organic Electronics,2012,13:1197. 14 Zheng X J, Peng Q M, Lin J, et al. Simultaneous harvesting of triplet excitons in OLEDs by both guest and host materials with an intramolecular charge-transfer feature via triplet-triplet annihilation[J].Journal of Material Chemistry C,2015,3:6970. 15 Simth G C. Triplet exaction phosphorescence in crystalline anthracene[J].Physical Reviews,1968,166(3):839. 16 Hu J Y, Pu J Y, Staoh F, et al. Bisanthracene-based donor-acceptor-type light-emitting-dopants: Highly efficient deep-blue emission in organic light emitting devices[J].Advanced Functional Materials,2014,24:2064. 17 Lee K H, Kang L K, Lee J Y, et al. Molecular engineering of blue fluorescent molecules based on silicon end-capped diphenylaminof-luorene derivatives for efficient organic light emitting materials[J].Advanced Functional Materials,2010,20(8):1345. 18 Duan L, Qiu Y. Recent advances inorganic electroluminescent materials and devices[J].Chinese Journal of Material Research,2015,29(5):321(in Chinese). 段炼,邱勇.有机发光材料与器件研究进展[J].材料研究学报,2015,9(5):321. 19 Endo A, Ogasawara M, Takahashi A, et al. Thermally activated delayed fluorescence from Sn4+-phrphyrin complexes and their application to organic light emitting diodes—A novel mechanism for electroluminescence[J].Advanced Materials,2009,21(47):4802. 20 Uoyama H, Goushi K, Shizu K, et al. Highly efficient organic light-emitting diodes from delayed flurescence[J].Nature,2012,492:234. 21 Lin T A, Chatterjee T, Tsai W L, et al. Sky-blue organic light emitting diode with 37% external quantum efficiency using thermally activated delayed fluorescence from Spiroacridine-triazinehybrid[J].Advanced Materials,2016,28:6976. 22 Kim M, Jeon S K, Hwang S H, et al. Stable blue thermally activated delayed fluorescent organic light-emitting diodes with three times longer lifetime than phosphorescent organic light-emitting diodes[J].Advanced Materials,2015,27(15):2515. 23 Zhang Q S, Li J, Shizu K, et al. Design of efficient thermally activated delayed fluorescence materials for pure blue organic light emitting diodes[J].Journal of American Chemistry Society,2012,134:14706. 24 Jankus V, et al. Deep blue exciplex organic light-emitting diodes with enhanced efficiency; p-type or e-type triplet conversion to singlet excitons?[J].Advanced Materials,2013,25:1455. 25 Endo A, Sato K, Yoshimura K, et al. Efficient up-conversion of triplet exctions into a singlet state and its application for organic light emitting diodes[J].Applied Physical Letters,2011,98:083302. 26 Tao Y, Yuan K, Chen T, et al. Thermally activated delayed fluorescence materials towards the breakthrough of organoelectronics[J].Advanced Materials,2014,26:7931. 27 Gao Y, Zhang S T, Pan Y Y, et al. Hybridization and de-hybridization between thelocally-excited (LE) state and the charge-transfer(CT) state: A combined experimental and theoretical study[J].Physical Chemistry Chemical Physics,2016,18:24176. 28 Zhang Q S, Li B, Huang S P, et al. Efficient blue organic light-emitting diodes employing thermally activated delayed fluorescence[J].Nature Photonics,2014,8:326. 29 Chen W C, Lee C S, Tong Q X. Blue-emitting organic electrofluorescence materials: Progress and prospective[J].Journal of Material Chemistry C,2015,3:10957. 30 Li W J, Liu D D, et al. A twisting donor-acceptor molecule with an intercrossed excited state for highly efficient, deep-blue electroluminescence[J].Advanced Functional Materials,2012,22:2797. 31 Liu H C, et al. Efficient deep-blue non-doped organic light emitting diode with improved roll-off of efficiency based on hybrid local and charge-transfer excited state[J].RSC Advanced,2016,6:70085. 32 Zhang S T, Li W J, Yao L, et al. Enhanced proportion of radiative excitons in non-doped electro-fluorescence generated from an imida-zole derivative with an orthogonal donor-acceptor structure[J].Che-mistry Communication,2013,49:11302. 33 Zhang S T, Yao L, Peng Q M, et al. Achieving a significantly increased efficiency in nondoped pure blue fluorescent OLED: A quasi-equivalent hybridized excited state[J].Advanced Functional Mate-rials,2015,25:1755.
渝公网安备50019002502923号 版权所有：《材料导报》编辑部
2018, Vol. 32 
