首页|Efficient Spin-Flip between Charge-Transfer States for High-Performance Electroluminescence,without an Intermediate Locally Excited State

Efficient Spin-Flip between Charge-Transfer States for High-Performance Electroluminescence,without an Intermediate Locally Excited State

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Thermally activated delayed fluorescence(TADF)materials with both high photoluminescence quantum yield(PLQY)and fast reverse intersystem crossing(RISC)are strongly desired to realize efficient and stable organic light-emitting diodes(OLEDs).Control of excited-state dynamics via molecular design plays a central role in optimizing the PLQY and RISC rate of TADF materials but remains challenging.Here,3 TADF emitters possessing similar molecular structures,similar high PLQYs(89.5％to 96.3％),and approximate energy levels of the lowest excited singlet states(S1),but significantly different spin-flipping RISC rates(0.03 × 106 s-1 vs.2.26 × 106 s-1)and exciton lifetime(297.1 to 332.8 μs vs.6.0 μs)were systematically synthesized to deeply investigate the feasibility of spin-flip between charge-transfer excited states(3CT-1CT)transition.Experimental and theoretical studies reveal that the small singlet-triplet energy gap together with low RISC reorganization energy between the 3CT and 1CT states could provide an efficient RISC through fast spin-flip 3CT-1CT transition,without the participation of an intermediate locally excited state,which has previously been recognized as being necessary for realizing fast RISC.Finally,the OLED based on the champion TADF emitter achieves a maximum external quantum efficiency of 27.1％,a tiny efficiency roll-off of 4.1％at 1,000 cd/m2,and a high luminance of 28,150 cd/m2,which are markedly superior to those of the OLEDs employing the other 2 TADF emitters.

Donghai Zhang、Shanshan Jiang、Xiaodong Tao、Fulin Lin、Lingyi Meng、Xu-Lin Chen、Can-Zhong Lu

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State Key Laboratory of Structural Chemistry,Fujian Institute of Research on the Structure of Matter,Chinese Academy of Sciences,Fuzhou,Fujian 350002,China

Fujian Science and Technology Innovation Laboratory for Optoelectronic Information of China,Fuzhou,Fujian 350108,China

Xiamen Key Laboratory of Rare Earth Photoelectric Functional Materials,Xiamen Institute of Rare Earth Materials,Haixi Institutes,Chinese Academy of Sciences,Xiamen,Fujian 361021,China

University of Chinese Academy of Sciences,Beijing 100

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国家自然科学基金国家自然科学基金福建省自然科学基金Fujian Science and Technology Innovation Laboratory for Optoelectronic Information of ChinaFujian Science and Technology Innovation Laboratory for Optoelectronic Information of ChinaYouth Innovation Foundation of Xiamen CityYouth Innovation Foundation of Xiamen City

52073286218052812006L20052021ZR1322021ZZ1153502Z202060823502Z20206083

2024

10.34133/research.0155

研究(英文)

研究(英文)

CSTPCD
ISSN：
年,卷(期)：2024.2024(1)
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