A gold(<scp>iii</scp>)–TADF emitter as a sensitizer for high-color-purity and efficient deep-blue solution-processed OLEDs

Zhou, Dongling; Wu, Siping; Cheng, Gang; Che, Chi‐Ming

doi:10.1039/d1tc05487b

Cited by 26 publications

(24 citation statements)

References 44 publications

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“…To the best of our knowledge, this performance is the best result for solution‐processed blue MR‐TADF OLEDs (Figure S10 and Table S6, Supporting Information). [ 10,20,34–37 ] On the contrary, the EQE at 1000 cd m −2 of 5CzTRZ sensitized device and nonsensitized device could only reach 16.4% and 2.7%, suggesting large roll‐off value of 24.4% and 86.0%. The extremely large efficiency roll‐off for nonsensitized device could be safely ascribed to serious triplet exciton quenching induced by the slow triplet exciton conversion on the MR‐TADF emitter.…”

Section: Resultsmentioning

confidence: 99%

“…[ 40–48 ] However, this approach has not successfully achieved promising device performance in solution‐processed MR‐TADF OLEDs, due to the lack of solution‐processible TADF sensitizers with high RISC rate. [ 37 ]…”

Section: Introductionmentioning

confidence: 99%

“…[24][25][26][27][28][29][30][31][32][33] However, the device performance of solution-processed MR-TADF OLEDs remains far away from that of their vacuum-deposited counterparts. Especially, the efficiency roll-off at high luminance is very large, [6,10,20,[34][35][36][37] which hinders its practical application.…”

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confidence: 99%

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Achieving Efficient Solution‐Processed Blue Narrowband Emitting OLEDs with Small Efficiency Roll‐Off by Using a Bulky TADF Sensitizer with High Reverse Intersystem Crossing Rate

Chen

Chang

Shu

et al. 2022

Advanced Optical Materials

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emitters exhibit good color purity with small full width at half maximum (FWHM) of electroluminescent spectra, which promises next-generation ultrahighdefinition display. Up to now, most of the high-performance MR-TADF OLEDs were fabricated by vacuum deposition, [7] which requires expensive equipment and excessive energy consumption. Solutionprocessing methods have special advantages, such as large-area and low-cost manufacturing, which is a more economical approach for the mass production of OLED displays. [24][25][26][27][28][29][30][31][32][33] However, the device performance of solution-processed MR-TADF OLEDs remains far away from that of their vacuum-deposited counterparts. Especially, the efficiency roll-off at high luminance is very large, [6,10,20,[34][35][36][37] which hinders its practical application.The MR-TADF emitters usually have a moderate singlet-triplet energy splitting (ΔE ST ), [1,11,[19][20][21][22] which results in slow reverse intersystem crossing (RISC) process. So, the conversion of triplet excitons to singlet ones on MR-TADF emitters is inefficient. And the large number of unconverted triplet excitons would accumulate at the light-emitting layer (EML) to induce triplet-triplet annihilation (TTA) and triplet-polaron annihilation (TPA). The triplet exciton annihilation becomes even more serious at practical luminance with high exciton density, which leads to large efficiency roll-off. [38,39] This problem could be solved by codoping a thermally activated delayed fluorescent (TADF) material with high RISC rate in the EML as the sensitizer for the MR-TADF emitters. [15] The triplet excitons could be converted to singlet ones rapidly on the sensitizer, and then transfer to the MR-TADF emitter through long-range Förster resonance energy transfer (FRET) for narrowband emission. [17] With this approach, a lot of high-performance vacuumdeposited MR-TADF OLEDs have been reported by developing efficient TADF sensitizers. [40][41][42][43][44][45][46][47][48] However, this approach has not successfully achieved promising device performance in solution-processed MR-TADF OLEDs, due to the lack of solutionprocessible TADF sensitizers with high RISC rate. [37] Solution-processed organic light-emitting diodes (OLEDs) based on multipleresonance thermally activated delayed fluorescence (MR-TADF) emitters exhibit high color purity for next-generation ultrahigh-definition display. However, they suffer from low efficiency and large efficiency roll-off due to slow triplet exciton upconversion of MR-TADF emitters, resulting in serious triplet exciton quenching. Here, efficient solution-processed blue MR-TADF OLEDs featured with small efficiency roll-off are developed by using a new bulky TADF sensitizer consisting of five di-tert-butylcarbazoles and one triazine with high reverse intersystem crossing rate of 2.0 × 10 7 s −1 , which can rapidly convert triplet excitons to singlet ones to avoid exciton quenching. The Dexter energy transfer from the sensitizer to the MR-TADF emitter is blocked by using tertiary b...

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Achieving Efficient Solution‐Processed Blue Narrowband Emitting OLEDs with Small Efficiency Roll‐Off by Using a Bulky TADF Sensitizer with High Reverse Intersystem Crossing Rate

Chen

Chang

Shu

et al. 2022

Advanced Optical Materials

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“…In brief, we treat the studied Ir(III) complexes as a phosphor with a good transition dipole so that the triplet-to-singlet FRET is operative. This FRET process has proven to be feasible in a number of reports. ,, Based on an emitting layer consisting of PPT:20 wt % f -Ir(mfcp) 3 :1 wt % ν DABNA, relevant kinetic derivations lead to an energy transfer model proposed in Scheme S1. As a result, the overall energy transfer rate constant and efficiency are deduced to be 5.3 × 10 6 s –1 and 85%, respectively.…”

Section: Resultsmentioning

confidence: 99%

Engineering of Cyano Functionalized Benzo[d]imidazol-2-ylidene Ir(III) Phosphors for Blue Organic Light-Emitting Diodes

Yan

Wang

Hsu

et al. 2023

ACS Appl. Mater. Interfaces

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In this study, we designed and synthesized three series of blue emitting homoleptic iridium(III) phosphors bearing 4(5-mfcp) cyclometalates, respectively. These iridium complexes exhibit intense phosphorescence in the high energy region of 435−513 nm in the solution state at RT, to which the relatively large T 1 → S 0 transition dipole moment is beneficial for serving as a pure emitter and an energy donor to the multiresonance thermally activated delayed fluorescence (MR-TADF) terminal emitters via Forster resonance energy transfer (FRET). The resulting OLEDs achieved true blue, narrow bandwidth EL with a max EQE of 16−19% and great suppression of efficiency rolloff with ν-DABNA and t-DABNA. We obtained the FRET efficiency up to 85% using titled Ir(III) phosphors f-Ir(mfcp) 3 and f-Ir(5-mfcp) 3 to achieve true blue narrow bandwidth emission. Importantly, we also provide analysis on the kinetic parameters involved in the energy transfer processes and, accordingly, propose feasible ways to improve the efficiency roll-off caused by the shortened radiative lifetime of hyperphosphorescence.

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“…The low operational stability may be due to the instability of PEDOT:PSS during continuous operation and the lack of optimization of the device structure for lifetime evaluation. 4 d ,13 Considering that WOLEDs with an operationally stable EL spectrum would appeal to lighting applications, the EL spectra of the aforementioned two WOLEDs were recorded before and after the device lifetime measurement. The normalized EL spectrum of the WOLED containing Au-7 remained identical before and after the measurement (Fig.…”

Section: Resultsmentioning

confidence: 99%

Solution-processed single-emissive-layer WOLEDs with high efficiency and ultra-high color rendering index beyond 90

et al. 2023

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A gold(iii)–TADF emitter as a sensitizer for high-color-purity and efficient deep-blue solution-processed OLEDs

Abstract: Herein is described a blue-emitting gold(III)-TADF complex Au-1 that could act as a sensitizer for a solution-processed organic light-emitting diode (SP-OLED), in which a multi-resonance TADF emitter ν-DABNA is employed...

Cited by 26 publications

References 44 publications

Achieving Efficient Solution‐Processed Blue Narrowband Emitting OLEDs with Small Efficiency Roll‐Off by Using a Bulky TADF Sensitizer with High Reverse Intersystem Crossing Rate

Achieving Efficient Solution‐Processed Blue Narrowband Emitting OLEDs with Small Efficiency Roll‐Off by Using a Bulky TADF Sensitizer with High Reverse Intersystem Crossing Rate

Engineering of Cyano Functionalized Benzo[d]imidazol-2-ylidene Ir(III) Phosphors for Blue Organic Light-Emitting Diodes

Solution-processed single-emissive-layer WOLEDs with high efficiency and ultra-high color rendering index beyond 90

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