Yongjun Song, Ke Zhang, Pingping Wang, Yuan Cao, Lei He
{"title":"通过平面供体实现强分子间电荷转移(TSCT),同时改善空间约束的穿越空间电荷转移(TSCT)发射器中的辐射衰减和反向系间穿越","authors":"Yongjun Song, Ke Zhang, Pingping Wang, Yuan Cao, Lei He","doi":"10.1002/adfm.202411957","DOIUrl":null,"url":null,"abstract":"Simultaneously improving radiative decay and reverse intersystem crossing (RISC) of through-space charge-transfer (TSCT) thermally-activated delayed fluorescence (TADF) emitters has remained a challenge. Here, space-confined TSCT-TADF emitters are developed with a planar indolo[3,2,1-<i>kl</i>]phenoxazine donor, a spiro-carbon-fixed benzophenone acceptor, and a fluorene (for <b>1</b>) or xanthene (for <b>2</b>) bridge. Close, cofacial donor/acceptor alignments and efficient intramolecular TSCT have been observed for both emitters. Intriguingly, emitter <b>1</b> exhibits an intermolecular donor/acceptor interaction as strong as the intramolecular one, which opens efficient intermolecular TSCT, improving the radiative decay rate (<i>k</i><sub>r,s</sub>) to the same level as emitter <b>2</b> featuring a much stronger intramolecular donor/acceptor interaction. The intermolecular TSCT also largely enhances the RISC rate (<i>k</i><sub>RISC</sub>). In the 20 wt.% doped films, emitters <b>1</b> and <b>2</b> show green TADF with high <i>k</i><sub>r,s</sub>/<i>k</i><sub>RISC</sub> at 1.1 × 10<sup>7</sup> s<sup>−1</sup>/1.3 × 10<sup>6</sup> s<sup>−1</sup> and 1.2 × 10<sup>7</sup> s<sup>−1</sup>/7.7 × 10<sup>5</sup> s<sup>−1</sup>, respectively. Organic light–emitting diodes (OLEDs) using the emitters show high external quantum efficiencies (EQEs) up to 27.5% and low-efficiency roll-offs. Hyperfluorescent OLEDs using the emitters as sensitizers afford narrowband blue-green emission with high EQEs up to 30.6% and largely suppressed efficiency roll-offs. The work reveals that strengthening intermolecular TSCT is a promising avenue to simultaneously improve <i>k</i><sub>r,s,</sub> and <i>k</i><sub>RISC</sub> of TSCT-TADF emitters for high-performance OLEDs.","PeriodicalId":112,"journal":{"name":"Advanced Functional Materials","volume":null,"pages":null},"PeriodicalIF":18.5000,"publicationDate":"2024-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Simultaneously Improving Radiative Decay and Reverse Intersystem Crossing in Space-Confined Through-Space Charge-Transfer (TSCT) Emitter by Strong Intermolecular TSCT Enabled by a Planar Donor\",\"authors\":\"Yongjun Song, Ke Zhang, Pingping Wang, Yuan Cao, Lei He\",\"doi\":\"10.1002/adfm.202411957\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"Simultaneously improving radiative decay and reverse intersystem crossing (RISC) of through-space charge-transfer (TSCT) thermally-activated delayed fluorescence (TADF) emitters has remained a challenge. Here, space-confined TSCT-TADF emitters are developed with a planar indolo[3,2,1-<i>kl</i>]phenoxazine donor, a spiro-carbon-fixed benzophenone acceptor, and a fluorene (for <b>1</b>) or xanthene (for <b>2</b>) bridge. Close, cofacial donor/acceptor alignments and efficient intramolecular TSCT have been observed for both emitters. Intriguingly, emitter <b>1</b> exhibits an intermolecular donor/acceptor interaction as strong as the intramolecular one, which opens efficient intermolecular TSCT, improving the radiative decay rate (<i>k</i><sub>r,s</sub>) to the same level as emitter <b>2</b> featuring a much stronger intramolecular donor/acceptor interaction. The intermolecular TSCT also largely enhances the RISC rate (<i>k</i><sub>RISC</sub>). In the 20 wt.% doped films, emitters <b>1</b> and <b>2</b> show green TADF with high <i>k</i><sub>r,s</sub>/<i>k</i><sub>RISC</sub> at 1.1 × 10<sup>7</sup> s<sup>−1</sup>/1.3 × 10<sup>6</sup> s<sup>−1</sup> and 1.2 × 10<sup>7</sup> s<sup>−1</sup>/7.7 × 10<sup>5</sup> s<sup>−1</sup>, respectively. Organic light–emitting diodes (OLEDs) using the emitters show high external quantum efficiencies (EQEs) up to 27.5% and low-efficiency roll-offs. Hyperfluorescent OLEDs using the emitters as sensitizers afford narrowband blue-green emission with high EQEs up to 30.6% and largely suppressed efficiency roll-offs. The work reveals that strengthening intermolecular TSCT is a promising avenue to simultaneously improve <i>k</i><sub>r,s,</sub> and <i>k</i><sub>RISC</sub> of TSCT-TADF emitters for high-performance OLEDs.\",\"PeriodicalId\":112,\"journal\":{\"name\":\"Advanced Functional Materials\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":18.5000,\"publicationDate\":\"2024-09-20\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Advanced Functional Materials\",\"FirstCategoryId\":\"88\",\"ListUrlMain\":\"https://doi.org/10.1002/adfm.202411957\",\"RegionNum\":1,\"RegionCategory\":\"材料科学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q1\",\"JCRName\":\"CHEMISTRY, MULTIDISCIPLINARY\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Advanced Functional Materials","FirstCategoryId":"88","ListUrlMain":"https://doi.org/10.1002/adfm.202411957","RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"CHEMISTRY, MULTIDISCIPLINARY","Score":null,"Total":0}
Simultaneously Improving Radiative Decay and Reverse Intersystem Crossing in Space-Confined Through-Space Charge-Transfer (TSCT) Emitter by Strong Intermolecular TSCT Enabled by a Planar Donor
Simultaneously improving radiative decay and reverse intersystem crossing (RISC) of through-space charge-transfer (TSCT) thermally-activated delayed fluorescence (TADF) emitters has remained a challenge. Here, space-confined TSCT-TADF emitters are developed with a planar indolo[3,2,1-kl]phenoxazine donor, a spiro-carbon-fixed benzophenone acceptor, and a fluorene (for 1) or xanthene (for 2) bridge. Close, cofacial donor/acceptor alignments and efficient intramolecular TSCT have been observed for both emitters. Intriguingly, emitter 1 exhibits an intermolecular donor/acceptor interaction as strong as the intramolecular one, which opens efficient intermolecular TSCT, improving the radiative decay rate (kr,s) to the same level as emitter 2 featuring a much stronger intramolecular donor/acceptor interaction. The intermolecular TSCT also largely enhances the RISC rate (kRISC). In the 20 wt.% doped films, emitters 1 and 2 show green TADF with high kr,s/kRISC at 1.1 × 107 s−1/1.3 × 106 s−1 and 1.2 × 107 s−1/7.7 × 105 s−1, respectively. Organic light–emitting diodes (OLEDs) using the emitters show high external quantum efficiencies (EQEs) up to 27.5% and low-efficiency roll-offs. Hyperfluorescent OLEDs using the emitters as sensitizers afford narrowband blue-green emission with high EQEs up to 30.6% and largely suppressed efficiency roll-offs. The work reveals that strengthening intermolecular TSCT is a promising avenue to simultaneously improve kr,s, and kRISC of TSCT-TADF emitters for high-performance OLEDs.
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