Realizing External Quantum Efficiency over 25% with Low Efficiency Roll-Off in Polymer-Based Light-Emitting Diodes Synergistically Utilizing Intramolecular Sensitization and Bipolar Thermally Activated Delayed Fluorescence Monomer

Liu, Yuchao; Xie, Yanchao; Liu, Hua; Tong, Xingwen; Ying, Shian; Ren, Zhongjie; Yan, Shouke

doi:10.31635/ccschem.022.202201900

Cited by 21 publications

(28 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…23 Liu et al found that by properly adjusting the ratio between the host units, TADF emitters and sensitizers, the final solution-processed OLED reached a maximum EQE of 25.4% at 1000 cd m À2 , which is the highest efficiency among OLED devices based on TADF polymers at high brightness. 24 As for the side-chain TADF polymers, a series of copolymers with bulky spacer units and pendant TADF groups have been developed. [25][26][27][28][29] By up-loading the bulky spacer contents, Bryce and coworkers also demonstrate that a non-conjugated side-chain TADF polymer also can achieve a high EQE of 20.1%.…”

Section: Introductionmentioning

confidence: 99%

Combining molecular encapsulation and an AIE strategy to construct an efficient blue TADF polymer for solution-processed multilayer white OLEDs

Ban

Zhou²,

Cao³

et al. 2022

J. Mater. Chem. C

View full text Add to dashboard Cite

show abstract

Section: Introductionmentioning

confidence: 99%

Combining molecular encapsulation and an AIE strategy to construct an efficient blue TADF polymer for solution-processed multilayer white OLEDs

Ban

Zhou²,

Cao³

et al. 2022

J. Mater. Chem. C

View full text Add to dashboard Cite

show abstract

“…The high PLQY and the matched exciton dynamics of HCP-7.5% exhibited in photoluminescence promise its potential excellent EL. Additionally, in Figures e and S6, the lifetimes and proportions of delayed components for the HCPs prominently improve with the elevated temperatures, and therefore the predictable TADF characteristic can be unambiguously verified . The Arrhenius equation was then used to further investigate the temperature dependence of k RISC , and the Δ E ST values of emitters are quantitatively determined by an approximate value of the activation energies for RISC (ΔE a RISC ).…”

Section: Results and Discussionmentioning

confidence: 96%

“…Additionally, in Figures 3e and S6, the lifetimes and proportions of delayed components for the HCPs prominently improve with the elevated temperatures, and therefore the predictable TADF characteristic can be unambiguously verified. 47 The Arrhenius equation was then used to further investigate the temperature dependence of k RISC , and the ΔE ST values of emitters are quantitatively determined by an approximate value of the activation energies for RISC (ΔE aRISC ). Because of the intrinsically endothermic nature of the RISC process, ΔE a RISC s of the designed HCPs reveal a positive temperature dependence.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Hyperbranched Conjugated Polymer with Multiple Charge Transfer Enables High-Efficiency Nondoped Red Electroluminescence with Low Driving Voltage

Zhao

Tong

Liu

et al. 2023

ACS Appl. Mater. Interfaces

Self Cite

View full text Add to dashboard Cite

Conjugated polymers featuring thermally activated delayed fluorescence (TADF) attract tremendous attention in both academic and industry communities due to their easy solution processing for fabricating large-area and low-cost high-performance polymer light-emitting diodes (PLEDs). However, current nondoped solution-processed PLEDs frequently encounter significant efficiency roll-offs and unreasonably high operating voltages at high brightness, especially for red-emitting polymers. Herein, we design hyperbranched conjugated polymers (HCPs) with D−A−D type TADF characteristics for high-performance red-emitting PLEDs. Multiple intramolecular charge transfer (ICT) channels induced by quasi-equivalent donors of the TADF core strongly boost the reverse intersystem crossing (RISC) process and singlet excitons radiative transition. Coupling with the efficient energy transfer process generated by structure advantages of HCPs, the strongly electron-withdrawing oxygen atoms located on the TADF cores further accelerate hole transportation from the host chains to the TADF cores. Under a rational regulation of the TADF core ratio, the related nondoped red-emitting device performs an outstanding performance with an EQE max of 8.39% and exhibits no roll-off while the luminance is less than 100 cd/m 2 and only 3.3% decrease at 500 cd/m 2 . Simultaneously, the EQE can maintain 7.4% under 1000 cd/m 2 . Furthermore, the corresponding nondoped device exhibits a low turn-on voltage of around 2.5 V and achieves a luminance of 500 cd/m 2 at 3.5 V and even 1000 cd/m 2 at 3.9 V. To our knowledge, this is the best performance among all nondoped red PLEDs with high brightness obtained at low operating voltage.

show abstract

“…Recently, we have improved the performance of TADF polymeric materials by synergistically utilizing intramolecular sensitization and the bipolar TADF monomer (Figure 3a). 23 Through vibrational coupling between 1 CT and 3 CT involving two distinct electron acceptors and the conjugated backbone (Figure 3b), triplet excitons are efficiently transformed into singlet states with different energies. The accumulated singlet excitons are subsequently transferred to emissive states from TADF-type sensitizers via favorable Forster resonance energy transfer (FRET), utilizing the sophisticated hyperfluorescent system proposed in pioneering studies.…”

Section: Of the Conjugated Polymeric Backbones By Copolymerizing The ...mentioning

confidence: 99%

Regulating the Nature of Triplet Excited States of Thermally Activated Delayed Fluorescence Emitters

2023

Self Cite

View full text Add to dashboard Cite

Conspectus Characterized by the reverse intersystem crossing (RISC) process from the triplet state (T1) to the singlet state (S1), thermally activated delayed fluorescence (TADF) emitters, which produce light by harvesting both triplet and singlet excitons without noble metals, are considered to be third-generation organic electroluminescent materials. Rapid advances in molecular design criteria, understanding the photophysics underlying TADF, and applications of TADF materials as emitters in organic light-emitting diodes (OLEDs) have been achieved. Theoretically, enhanced spin–orbit coupling (SOC) between singlet and triplet states can result in a fast RISC process and thus a high light-emitting efficiency according to Fermi’s golden rule. Therefore, regulating the nature of triplet excited states by elaborate molecular design to improve SOC is an effective approach to high-efficiency TADF-based OLEDs. Generally, on one hand, the increased local excited (LE) populations of the excited triplet state can significantly improve the nature flips between S1 and T1. On other hand, the reduced energy gap between S1 and the lowest triplet with a charge transfer (CT) characteristic can also enhance their vibronic coupling. Consequently, it is vital to determine how to regulate the nature of triplet excited states by molecular design to guide the material synthesis, especially for polymeric emitters. In this Account, we focus on modulating the strategy of triplet excited states for TADF emitters and an in-depth understanding of the photophysical processes, leading to optimized OLED device performance. We include several kinds of strategies to control the nature of triplet excited states to guide the synthesis of small-molecule and polymer TADF emitters: (1) Modulating the electronic distribution of conjugated polymeric backbones by copolymerizing the electron-donating host: accordingly, the nature of excited states can be changed, especially for triplets. Meanwhile, the utilization of excitons can be systematically improved by adjusting the electronic structure of triplet states with long-range distribution in the conjugated polymeric backbones. (2) Halogenating acceptors of TADF units: the introduced halogen atoms would reestablish the electronic distribution of the triplet and relocate the hole orbits, resulting in a CT and LE hybrid nature of a triplet transformed into a LE-predominant state, which favors the RISC process. (3) Stereostructure regulation: by constructing a diverse arrangement of three-dimensional spatial configurations or conjugated architectures, the nature of the triplet can also be finely tuned, such as hyperbranched structures with multiple triplet–singlet vibration couplings, half-dendronized–half-encapsulated asymmetric systems, trinaphtho[3,3,3] propeller-based three-dimensional spatial interspersed structures, intramolecular close-packed donor–acceptor systems, and so on. We hope that this Account will provide insights into new structures and mechanisms for achieving high-performance OLEDs base...

show abstract

Realizing External Quantum Efficiency over 25% with Low Efficiency Roll-Off in Polymer-Based Light-Emitting Diodes Synergistically Utilizing Intramolecular Sensitization and Bipolar Thermally Activated Delayed Fluorescence Monomer

Cited by 21 publications

References 0 publications

Combining molecular encapsulation and an AIE strategy to construct an efficient blue TADF polymer for solution-processed multilayer white OLEDs

Combining molecular encapsulation and an AIE strategy to construct an efficient blue TADF polymer for solution-processed multilayer white OLEDs

Hyperbranched Conjugated Polymer with Multiple Charge Transfer Enables High-Efficiency Nondoped Red Electroluminescence with Low Driving Voltage

Regulating the Nature of Triplet Excited States of Thermally Activated Delayed Fluorescence Emitters

Contact Info

Product

Resources

About