1
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Jung YH, Lee GS, Muruganantham S, Kim HR, Oh JH, Ham JH, Yadav SB, Lee JH, Chae MY, Kim YH, Kwon JH. Modified t-butyl in tetradentate platinum (II) complexes enables exceptional lifetime for blue-phosphorescent organic light-emitting diodes. Nat Commun 2024; 15:2977. [PMID: 38582788 PMCID: PMC10998867 DOI: 10.1038/s41467-024-47307-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Accepted: 03/26/2024] [Indexed: 04/08/2024] Open
Abstract
In blue phosphorescent dopants, the tetradentate platinum(II) complex is a promising material showing high efficiency and stability in devices. However, metal-metal-to-ligand charge transfer (MMLCT) formation leads to low photo-luminescence quantum yields (PLQYs), wide spectra, and intermolecular interaction. To suppress MMLCT, PtON-tb-TTB and PtON-tb-DTB are designed using theoretical simulation by modifying t-butyl in PtON-TBBI. Both materials effectively suppress MMLCT and exhibit high PLQYs of 99% and 78% in 5 wt% doped film, respectively. The PtON-tb-TTB and PtON-tb-DTB devices have maximum external quantum efficiencies of 26.3% and 20.9%, respectively. Additionally, the PtON-tb-DTB device has an extended lifetime of 169.3 h with an initial luminescence of 1200 nit, which is 8.5 times greater than the PtON-TBBI device. Extended lifetime because of suppressed MMLCT and smaller displacement between the lowest triplet and triplet metal-centered states compared to other dopants. The study provides an effective approach to designing platinum(II) complexes for long device lifetimes.
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Affiliation(s)
- Young Hun Jung
- Organic Optoelectronic Device Lab (OODL), Department of Information Display, Kyung Hee University, Seoul, Republic of Korea
| | - Gyeong Seok Lee
- Department of Chemistry and RIMA, Gyeongsang National University, Jinju, Republic of Korea
| | - Subramanian Muruganantham
- Organic Optoelectronic Device Lab (OODL), Department of Information Display, Kyung Hee University, Seoul, Republic of Korea
| | - Hye Rin Kim
- Organic Optoelectronic Device Lab (OODL), Department of Information Display, Kyung Hee University, Seoul, Republic of Korea
| | - Jun Hyeog Oh
- Organic Optoelectronic Device Lab (OODL), Department of Information Display, Kyung Hee University, Seoul, Republic of Korea
| | - Jung Ho Ham
- Organic Optoelectronic Device Lab (OODL), Department of Information Display, Kyung Hee University, Seoul, Republic of Korea
| | - Sagar B Yadav
- Organic Optoelectronic Device Lab (OODL), Department of Information Display, Kyung Hee University, Seoul, Republic of Korea
| | - Ji Hyun Lee
- Department of Chemistry and RIMA, Gyeongsang National University, Jinju, Republic of Korea
| | - Mi Young Chae
- Organic Optoelectronic Device Lab (OODL), Department of Information Display, Kyung Hee University, Seoul, Republic of Korea
| | - Yun-Hi Kim
- Department of Chemistry and RIMA, Gyeongsang National University, Jinju, Republic of Korea.
| | - Jang Hyuk Kwon
- Organic Optoelectronic Device Lab (OODL), Department of Information Display, Kyung Hee University, Seoul, Republic of Korea.
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2
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Li H, Qin J, Xian S, Tang H, Jiao Y, Zhang M, Wang L, Zhou Q, Wang Z. Hybrid nanospheres of silica covalently containing yellow-emitting cationic iridium(III) complex: preparation and application in white light-emitting diodes. Dalton Trans 2024; 53:4080-4087. [PMID: 38314631 DOI: 10.1039/d3dt03763k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2024]
Abstract
A yellow-emitting cationic iridium(III) complex [(dfppy)2Ir(TBD)]PF6 (TBD: N4,N4'-bis(3-(triethoxysilyl)propyl)-[2,2'-bipyridine]-4,4'-dicarboxamide; dfppy: 2-(2,4-difluorophenyl)pyridine) containing hydrolysable alkoxysilanes was synthesized. Then, a series of silica-based hybrid nanospheres with diameters of around 400 nm was prepared via the hydrolysis of this complex together with tetraethyl orthosilicate (TEOS, a silica source). When the amount of the complex used was 5.0 wt%, hybrid nanospheres showed the best photoluminescence (PL) properties, relative to the PL quantum yield of pure solid [(dfppy)2Ir(TBD)]PF6 (12.7%), that of hybrid nanospheres increased to 26.2%. Moreover, the thermal decomposition temperature (Td) of pure solid [(dfppy)2Ir(TBD)]PF6 was 331 °C, the Td of the complex in hybrid nanospheres increased to 447 °C. However, the yellow light emission was almost unchanged and was still located at 500-750 nm with a maximum wavelength (λem,max) of 577 nm. Under the excitation of blue-emitting chips (λem,max ≈ 455 nm), cold/neutral/warm white light-emitting diodes (WLEDs) with good luminous quality can all be fabricated using these hybrid nanospheres as phosphors in epoxy resin at different blending concentrations. Compared with two or three iridium(III) complexes being contained in silica-based particles as phosphors as described in literatures, in this study, silica-based hybrid nanospheres covalently containing only one yellow-emitting cationic iridium(III) complex as phosphors provide a more effective and simpler method for preparation high-performance WLEDs.
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Affiliation(s)
- Haoju Li
- Key Laboratory of Green-Chemistry Materials in University of Yunnan Province, National and Local Joint Engineering Research Center for Green Preparation Technology of Biobased Materials, School of Chemistry & Environment, Yunnan Minzu University, Kunming, 650500, P. R. China.
- School of Materials and Energy, Guangdong University of Technology, No. 100 Waihuan Xi Road, Guangzhou Higher Education Mega Center, Guangzhou 510006, China
| | - Jing Qin
- Key Laboratory of Green-Chemistry Materials in University of Yunnan Province, National and Local Joint Engineering Research Center for Green Preparation Technology of Biobased Materials, School of Chemistry & Environment, Yunnan Minzu University, Kunming, 650500, P. R. China.
| | - Shanglan Xian
- Key Laboratory of Green-Chemistry Materials in University of Yunnan Province, National and Local Joint Engineering Research Center for Green Preparation Technology of Biobased Materials, School of Chemistry & Environment, Yunnan Minzu University, Kunming, 650500, P. R. China.
| | - Huaijun Tang
- Key Laboratory of Green-Chemistry Materials in University of Yunnan Province, National and Local Joint Engineering Research Center for Green Preparation Technology of Biobased Materials, School of Chemistry & Environment, Yunnan Minzu University, Kunming, 650500, P. R. China.
| | - Yuxiang Jiao
- Key Laboratory of Green-Chemistry Materials in University of Yunnan Province, National and Local Joint Engineering Research Center for Green Preparation Technology of Biobased Materials, School of Chemistry & Environment, Yunnan Minzu University, Kunming, 650500, P. R. China.
| | - Meifang Zhang
- Institute of Carbon Neutral New Energy Research, Yuzhang Normal University, Nanchang 330031, China.
| | - Long Wang
- Key Laboratory of Green-Chemistry Materials in University of Yunnan Province, National and Local Joint Engineering Research Center for Green Preparation Technology of Biobased Materials, School of Chemistry & Environment, Yunnan Minzu University, Kunming, 650500, P. R. China.
| | - Qiang Zhou
- Key Laboratory of Green-Chemistry Materials in University of Yunnan Province, National and Local Joint Engineering Research Center for Green Preparation Technology of Biobased Materials, School of Chemistry & Environment, Yunnan Minzu University, Kunming, 650500, P. R. China.
| | - Zhengliang Wang
- Key Laboratory of Green-Chemistry Materials in University of Yunnan Province, National and Local Joint Engineering Research Center for Green Preparation Technology of Biobased Materials, School of Chemistry & Environment, Yunnan Minzu University, Kunming, 650500, P. R. China.
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3
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Wei YC, Kuo KH, Chi Y, Chou PT. Efficient Near-Infrared Luminescence of Self-Assembled Platinum(II) Complexes: From Fundamentals to Applications. Acc Chem Res 2023; 56:689-699. [PMID: 36882976 DOI: 10.1021/acs.accounts.2c00827] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/09/2023]
Abstract
ConspectusDesigning bright and efficient near-infrared (NIR) emitters has drawn much attention due to numerous applications ranging from biological imaging, medical therapy, optical communication, and night-vision devices. However, polyatomic organic and organometallic molecules with energy gaps close to the deep red and NIR regime are subject to dominant nonradiative internal conversion (IC) processes, which drastically reduces the emission intensity and exciton diffusion length of organic materials and hence hampers the optoelectronic performances. To suppress nonradiative IC rates, we suggested two complementary approaches to solve the issues: exciton delocalization and molecular deuteration. First, exciton delocalization efficiently suppresses the molecular reorganization energy through partitioning to all aggregated molecules. According to the IC theory together with the effect of exciton delocalization, the simulated nonradiative rates with the energy gap ΔE = 104 cm-1 decrease by around 104 fold when the exciton delocalization length equals 5 (promoting vibronic frequency ωl = 1500 cm-1). Second, molecular deuterations reduce Franck-Condon vibrational overlaps and vibrational frequencies of promoting modes, which decreases IC rates by 1 order of magnitude in comparison to the rates of nondeuterated molecules under ΔE of 104 cm-1. Although deuteration of molecules has long been attempted to increase emission intensity, the results have been mixed. Here, we provide a robust derivation of the IC theory to demonstrate its validity, especially to emission in the NIR region.The concepts are experimentally verified by the strategic design and synthesis of a class of square-planar Pt(II) complexes, which form crystalline aggregates in vapor deposited thin films. The packing geometries are well characterized by the grazing angle X-ray diffraction (GIXD), showing domino-like packing arrangements with the short ππ separation of 3.4-3.7 Å. Upon photoexcitation, such closely packed assemblies exhibit intense NIR emission maximized in the 740-970 nm region through metal-metal-to-ligand charge transfer (MMLCT) transition with unprecedented photoluminescent quantum yield (PLQY) of 8-82%. To validate the existence of exciton delocalization, we applied time-resolved step-scan Fourier transform UV-vis spectroscopy to probe the exciton delocalization length of Pt(II) aggregates, which is 5-9 molecules (2.1-4.5 nm) assuming that excitons mainly delocalized along the direction of ππ stacking. According to the dependence of delocalization length vs simulated IC rates, we verify that the observed delocalization lengths contribute to the high NIR PLQY of the aggregated Pt(II) complexes. To probe the isotope effect, both partially and completely deuterated Pt(II) complexes were synthesized. For the case of the 970 nm Pt(II) emitter, the vapor deposited films of per-deuterated Pt(II) complexes exhibit the same emission peak as that of the nondeuterated one, whereas PLQY increases ∼50%. To put the fundamental studies into practice, organic light-emitting diodes (OLEDs) were fabricated with a variety of NIR Pt(II) complexes as the emitting layer, showing the outstanding external quantum efficiencies (EQEs) of 2-25% and the remarkable radiances 10-40 W sr-1 m-2 at 740-1002 nm. The prominent device performances not only successfully prove our designed concept but also reach a new milestone for highly efficient NIR OLED devices.This Account thus summarizes our approaches about how to boost the efficiency of the NIR emission of organic molecules from an in-depth fundamental basis, i.e., molecular design, photophysical characterization, and device fabrication. The concept of the exciton delocalization and molecular deuteration may also be applicable to a single molecular system to achieve efficient NIR radiance, which is worth further investigation in the future.
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Affiliation(s)
- Yu-Chen Wei
- Department of Chemistry, National Taiwan University, Taipei, 10617 Taiwan, R.O.C
| | - Kai-Hua Kuo
- Department of Chemistry, National Taiwan University, Taipei, 10617 Taiwan, R.O.C
| | - Yun Chi
- Department of Materials Science and Engineering, Department of Chemistry, and Center of Super-Diamond and Advanced Films, City University of Hong Kong, Kowloon Tong, 999077 Hong Kong SAR
| | - Pi-Tai Chou
- Department of Chemistry, National Taiwan University, Taipei, 10617 Taiwan, R.O.C
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4
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A theoretical analysis on the electron and energy transfer between host and guest materials in phosphor–doped OLED. J Photochem Photobiol A Chem 2022. [DOI: 10.1016/j.jphotochem.2022.114058] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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5
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Kim E, Park J, Jun M, Shin H, Baek J, Kim T, Kim S, Lee J, Ahn H, Sun J, Ko SB, Hwang SH, Lee JY, Chu C, Kim S. Highly efficient and stable deep-blue organic light-emitting diode using phosphor-sensitized thermally activated delayed fluorescence. SCIENCE ADVANCES 2022; 8:eabq1641. [PMID: 36240272 PMCID: PMC9565789 DOI: 10.1126/sciadv.abq1641] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/18/2022] [Accepted: 08/29/2022] [Indexed: 06/16/2023]
Abstract
Phosphorescent and thermally activated delayed fluorescence (TADF) blue organic light-emitting diodes (OLEDs) have been developed to overcome the low efficiency of fluorescent OLEDs. However, device instability, originating from triplet excitons and polarons, limits blue OLED applications. Here, we develop a phosphor-sensitized TADF emission system with TADF emitters to achieve high efficiency and long operational lifetime. Peripheral carbazole moieties are introduced in conventional multi-resonance-type emitters containing one boron atom. The triplet exciton density of the TADF emitter is reduced by facilitating reverse intersystem crossing, and the Förster resonant energy transfer rate from phosphor sensitizer is enhanced by high absorption coefficient of the emitters. The emitter exhibited an operational lifetime of 72.9 hours with Commission Internationale de L'Eclairage chromaticity coordinate y = 0.165, which was 6.6 times longer than those of devices using conventional TADF emitters.
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Affiliation(s)
- Eungdo Kim
- Materials Research Team, Display Research Center, Samsung Display, Giheung, Gyeonggi 17113, Republic of Korea
| | - Junha Park
- Materials Research Team, Display Research Center, Samsung Display, Giheung, Gyeonggi 17113, Republic of Korea
| | - Mieun Jun
- Materials Research Team, Display Research Center, Samsung Display, Giheung, Gyeonggi 17113, Republic of Korea
| | - Hyosup Shin
- Materials Research Team, Display Research Center, Samsung Display, Giheung, Gyeonggi 17113, Republic of Korea
| | - Jangyeol Baek
- Materials Research Team, Display Research Center, Samsung Display, Giheung, Gyeonggi 17113, Republic of Korea
| | - Taeil Kim
- Materials Research Team, Display Research Center, Samsung Display, Giheung, Gyeonggi 17113, Republic of Korea
| | - Seran Kim
- Materials Research Team, Display Research Center, Samsung Display, Giheung, Gyeonggi 17113, Republic of Korea
| | - Jiyoung Lee
- Materials Research Team, Display Research Center, Samsung Display, Giheung, Gyeonggi 17113, Republic of Korea
| | - Heechoon Ahn
- Materials Research Team, Display Research Center, Samsung Display, Giheung, Gyeonggi 17113, Republic of Korea
| | - Jinwon Sun
- Materials Research Team, Display Research Center, Samsung Display, Giheung, Gyeonggi 17113, Republic of Korea
| | - Soo-Byung Ko
- Materials Research Team, Display Research Center, Samsung Display, Giheung, Gyeonggi 17113, Republic of Korea
| | - Seok-Hwan Hwang
- Materials Research Team, Display Research Center, Samsung Display, Giheung, Gyeonggi 17113, Republic of Korea
| | - Jun Yeob Lee
- School of Chemical Engineering, Sungkyunkwan University, Suwon, Gyeonggi 16419, Republic of Korea
| | - Changwoong Chu
- Materials Research Team, Display Research Center, Samsung Display, Giheung, Gyeonggi 17113, Republic of Korea
| | - Sunghan Kim
- Materials Research Team, Display Research Center, Samsung Display, Giheung, Gyeonggi 17113, Republic of Korea
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6
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Jena S, Eyyathiyil J, Behera SK, Kitahara M, Imai Y, Thilagar P. Crystallization induced room-temperature phosphorescence and chiral photoluminescence properties of phosphoramides. Chem Sci 2022; 13:5893-5901. [PMID: 35685799 PMCID: PMC9132070 DOI: 10.1039/d2sc00990k] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2022] [Accepted: 04/06/2022] [Indexed: 11/21/2022] Open
Abstract
We report the design and synthesis of a series of room temperature phosphorescent phosphoramides TPTZPO, TPTZPS, and TPTZPSe with a donor (phenothiazine)-acceptor (P = X, X = O, S, and Se) architecture. All the compounds show structureless fluorescence with a nanosecond lifetime in dilute solutions. However, these compounds show dual fluorescence and room temperature phosphorescence (RTP) in the solid state. Both the intensity and energy of luminescence depend on the heteroatom attached to the phosphorus center. For example, compound TPTZPO with the P[double bond, length as m-dash]O unit exhibits fluorescence at a higher energy region than TPTZPS and TPTZPSe with the P[double bond, length as m-dash]S and P[double bond, length as m-dash]Se groups, respectively. Crystalline samples of TPTZPO, TPTZPS, and TPTZPSe show stronger RTP than the amorphous powder of respective compounds. Detailed steady-state, time-resolved photoluminescence and computational studies established that the 3n-π* state dominated by the phenothiazine moiety is the emissive state of these compounds. Although TPTZPS and TPTZPSe crystallized in the chiral space group, only TPTZPSe showed chiroptical properties in the solid state. The luminescence dissymmetry factor (g lum) value of TPTZPS is small and below the detection limit, and a CPL spectrum could not be observed for this compound.
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Affiliation(s)
- Satyam Jena
- Department of Inorganic and Physical Chemistry, Indian Institute of Science Bangalore India - 560012
| | - Jusaina Eyyathiyil
- Department of Inorganic and Physical Chemistry, Indian Institute of Science Bangalore India - 560012
| | - Santosh Kumar Behera
- Department of Inorganic and Physical Chemistry, Indian Institute of Science Bangalore India - 560012
| | - Maho Kitahara
- Department of Applied Chemistry, Faculty of Science and Engineering, Kindai University 3-4-1 Kowakae, Higashi-Osaka Osaka 577-8502 Japan
| | - Yoshitane Imai
- Department of Applied Chemistry, Faculty of Science and Engineering, Kindai University 3-4-1 Kowakae, Higashi-Osaka Osaka 577-8502 Japan
| | - Pakkirisamy Thilagar
- Department of Inorganic and Physical Chemistry, Indian Institute of Science Bangalore India - 560012
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7
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Qu B, Ding K, Sun K, Hou S, Morris S, Shtein M, Forrest SR. Fast Organic Vapor Phase Deposition of Thin Films in Light-Emitting Diodes. ACS NANO 2020; 14:14157-14163. [PMID: 33016696 DOI: 10.1021/acsnano.0c07017] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Fast deposition of thin films is essential for achieving low-cost, high-throughput phosphorescent organic light-emitting diode (PHOLED) production. In this work, we demonstrate rapid and uniform growth of semiconductor thin films by organic vapor phase deposition (OVPD). A green PHOLED comprising an emission layer (EML) grown at 50 Å/s with bis[2-(2-pyridinyl-N)phenyl-C](acetylacetonato)iridium(III) (Ir(ppy)2(acac)) doped into 4,4'-bis(N-carbazolyl)-1,1'-biphenyl (CBP) exhibits a maximum external quantum efficiency of 20 ± 1%. The morphology, charge transport properties, and radiative efficiency under optical and electrical excitation of the PHOLED EML are investigated as functions of the deposition rate via both experimental and theoretical approaches. The EML shows no evidence for gas phase nucleation of the organic molecules at deposition rates as high as 50 Å/s. However, the roll-off in quantum efficiency at high current progressively increases with deposition rate due to enhanced triplet-polaron annihilation. The roll-off results from accumulation of stress within the PHOLED EML that generates a high density of defect states. The defects, in turn, act as recombination sites for triplets and hole polarons, leading to enhanced triplet-polaron annihilation at high current. We introduce a void nucleation model to describe the film morphology evolution that is observed using electron microscopy.
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Affiliation(s)
- Boning Qu
- Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Kan Ding
- Department of Physics, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Kai Sun
- Michigan Center for Materials Characterization (MCMC), Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Shaocong Hou
- Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Steven Morris
- Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Max Shtein
- Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, United States
- Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Stephen R Forrest
- Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, United States
- Department of Physics, University of Michigan, Ann Arbor, Michigan 48109, United States
- Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109, United States
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8
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Zukun W, Wu R, Chen Z, Ye L, Li H, Zhu H. Ultrafast Electron Transfer Before Singlet Fission and Slow Triplet State Electron Transfer in Pentacene Single Crystal/C 60 Heterostructure. J Phys Chem A 2020; 124:4185-4192. [PMID: 32353232 DOI: 10.1021/acs.jpca.0c01791] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The singlet fission (SF) process converts one high-energy singlet exciton to two low-energy triplet excitons after absorbing one photon. Organic photovoltaic devices based on the SF process have shown great potential in solar energy conversion to exceed Shockley-Queisser limit. The key to SF photovoltaic devices requires efficient electron transfer (ET) from triplet exciton after SF, which is yet to be thoroughly investigated. Here, we performed thorough photophysical studies in 6,13-Bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene)/C60 heterostructures using TIPS-pentacene microsize single crystal as a well-defined model system. We show the SF process in TIPS-pentacene single crystal occurs by a two-step process, with triplet pair intermediates forming in 75 fs and then dissociating to non-interacting triplets in 1.6 ps. The SF process in single crystal is comparable to that in polycrystalline film. Importantly, we observe a considerable fraction of singlet excitons is quenched by ultrafast (<75 fs) interfacial ET prior to fission and no ET from triplet excitons in 1.5 ns time window. We confirm that the absence of ET is not limited by exciton diffusion but due to very slow (≫1.5 ns) interfacial ET from triplet exciton. The observations contradict expected singlet and triplet ET behaviors based on a simple two-state Marcus ET model and suggest long-range interfacial ET from delocalized photoexcitation. The ultrafast ET from singlet exciton before SF and slow ET from triplet exciton call for reconsideration and careful design of efficient SF photovoltaic devices.
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Affiliation(s)
- Wang Zukun
- Centre for Chemistry of High-Performance & Novel Materials, Department of Chemistry, Zhejiang University, Hangzhou 310027, Zhejiang, China
| | - Ruihan Wu
- MOE Key Laboratory of Macromolecule Synthesis and Functionalization, State Key Laboratory of Silicon Materials, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou 310027, P. R. China
| | - Zeng Chen
- Centre for Chemistry of High-Performance & Novel Materials, Department of Chemistry, Zhejiang University, Hangzhou 310027, Zhejiang, China
| | - Lei Ye
- Centre for Chemistry of High-Performance & Novel Materials, Department of Chemistry, Zhejiang University, Hangzhou 310027, Zhejiang, China
| | - Hanying Li
- MOE Key Laboratory of Macromolecule Synthesis and Functionalization, State Key Laboratory of Silicon Materials, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou 310027, P. R. China
| | - Haiming Zhu
- Centre for Chemistry of High-Performance & Novel Materials, Department of Chemistry, Zhejiang University, Hangzhou 310027, Zhejiang, China
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9
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High energy acceptor states strongly enhance exciton transfer between metal organic phosphorescent dyes. Nat Commun 2020; 11:1292. [PMID: 32157092 PMCID: PMC7064524 DOI: 10.1038/s41467-020-15034-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Accepted: 02/12/2020] [Indexed: 12/05/2022] Open
Abstract
Exciton management in organic light-emitting diodes (OLEDs) is vital for improving efficiency, reducing device aging, and creating new device architectures. In particular in white OLEDs, exothermic Förster-type exciton transfer, e.g. from blue to red emitters, plays a crucial role. It is known that a small exothermicity partially overcomes the spectral Stokes shift, enhancing the fraction of resonant donor-acceptor pair states and thus the Förster transfer rate. We demonstrate here a second enhancement mechanism, setting in when the exothermicity exceeds the Stokes shift: transfer to multiple higher-lying electronically excited states of the acceptor molecules. Using a recently developed computational method we evaluate the Förster transfer rate for 84 different donor–acceptor pairs of phosphorescent emitters. As a result of the enhancement the Förster radius tends to increase with increasing exothermicity, from around 1 nm to almost 4 nm. The enhancement becomes particularly strong when the excited states have a large spin-singlet character. Exciton management in phosphorescent organic light-emitting diodes is critical to the optimal design and performance of these devices. Here, the authors report a computational method to elucidate the enhancement in exothermic exciton transfer between different phosphorescent emitters.
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10
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Stachurska K, Grochowski P, Antosiewicz JM. Diffusional Encounter Rate Constants for Xanthone and 2-Naphthoic Acid by Flash Photolysis Experiments and Brownian Dynamics Simulations: Substantial Effects of Polarizability of the Triplet State. J Phys Chem B 2019; 123:9328-9342. [PMID: 31585039 DOI: 10.1021/acs.jpcb.9b07989] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Diffusional encounter rate constants, for xanthone and 2-naphthoic acid molecules in their triplet states with xanthone or 2-naphthoic acid molecules in their triplet or singlet states, were determined using nanosecond laser flash photolysis spectroscopy. Simultaneously, Brownian dynamics simulations were used to compute these rate constants for assumed models of encountering molecules. Altogether, a global fit to transient absorption progress curves, reporting populations of triplet state xanthone and triplet state 2-naphthoic acid molecules, allowed us to determine six diffusional encounter rate constants from our experiments. The most important result of this study is the detection of substantial effects of the electric polarizability of molecules in their triplet state, visible for xanthone triplet and 2-naphthoic acid ground states, a homo triplet-triplet annihilation of 2-naphthoic acid, and a hetero triplet-triplet annihilation for xanthone and 2-naphthoic acid.
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Affiliation(s)
- K Stachurska
- Division of Biophysics, Institute of Experimental Physics, Faculty of Physics , University of Warsaw , 5 Pasteura St. , Warsaw 02-093 , Poland
| | - P Grochowski
- Interdisciplinary Centre for Mathematical and Computational Modelling , University of Warsaw , 15/17 Tyniecka St. , Warsaw 02-630 , Poland
| | - J M Antosiewicz
- Division of Biophysics, Institute of Experimental Physics, Faculty of Physics , University of Warsaw , 5 Pasteura St. , Warsaw 02-093 , Poland
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11
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Kirch A, Gmelch M, Reineke S. Simultaneous Singlet-Singlet and Triplet-Singlet Förster Resonance Energy Transfer from a Single Donor Material. J Phys Chem Lett 2019; 10:310-315. [PMID: 30605341 PMCID: PMC6601631 DOI: 10.1021/acs.jpclett.8b03668] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
For almost 70 years, Förster resonance energy transfer (FRET) has been investigated, implemented into nowadays experimental nanoscience techniques, and considered in a manifold of optics, photonics, and optoelectronics applications. Here, we demonstrate for the first time simultaneous and efficient energy transfer from both donating singlet and triplet states of a single photoluminescent molecular species. Using a biluminescent donor that can emit with high yield from both excited states at room temperature allows application of the FRET framework to such a bimodal system. It serves as an exclusive model system where the spatial origin of energy transfer is exactly the same for both donating spin states involved. Of paramount significance are the facts that both transfers can easily be observed by eye and that Förster theory is successfully applied to state lifetimes spanning over 8 orders of magnitude.
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Affiliation(s)
- Anton Kirch
- Dresden
Integrated Center for Applied Physics and Photonic Materials (IAPP)
and Institute of Applied Physics, Technische
Universität Dresden, 01069 Dresden, Germany
| | - Max Gmelch
- Dresden
Integrated Center for Applied Physics and Photonic Materials (IAPP)
and Institute of Applied Physics, Technische
Universität Dresden, 01069 Dresden, Germany
| | - Sebastian Reineke
- Dresden
Integrated Center for Applied Physics and Photonic Materials (IAPP)
and Institute of Applied Physics, Technische
Universität Dresden, 01069 Dresden, Germany
- Center
for Advancing Electronics Dresden (cfaed), Technische Universität Dresden, 01069 Dresden, Germany
- E-mail: . Phone: +49 351 463 38686. Fax: +49 351 463
37065
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12
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Munson KT, Kennehan ER, Doucette GS, Asbury JB. Dynamic Disorder Dominates Delocalization, Transport, and Recombination in Halide Perovskites. Chem 2018. [DOI: 10.1016/j.chempr.2018.09.001] [Citation(s) in RCA: 81] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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13
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Zhang D, Song X, Cai M, Duan L. Blocking Energy-Loss Pathways for Ideal Fluorescent Organic Light-Emitting Diodes with Thermally Activated Delayed Fluorescent Sensitizers. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2018; 30:1705250. [PMID: 29280207 DOI: 10.1002/adma.201705250] [Citation(s) in RCA: 82] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Revised: 10/08/2017] [Indexed: 06/07/2023]
Abstract
Organic light-emitting diodes (OLEDs) based on thermally activated delayed fluorescence-sensitized fluorescence (TSF) offer the possibility of attaining an ultimate high efficiency with low roll-off utilizing noble-metal free, easy-to-synthesize, pure organic fluorescent emitters. However, the performances of TSF-OLEDs are still unsatisfactory. Here, TSF-OLEDs with breakthrough efficiencies even at high brightnesses by suppressing the competitive deactivation processes, including direct charge recombination on conventional fluorescent dopants (CFDs) and Dexter energy transfer from the host to the CFDs, are demonstrated. On the one hand, electronically inert terminal-substituents are introduced to protect the electronically active core of the CFDs; on the other hand, delicate device structures are designed to provide multiple energy-funneling paths. As a result, unprecedentedly high maximum external quantum efficiency/power efficiency of 24%/71.4 lm W-1 in a green TSF-OLED are demonstrated, which remain at 22.6%/52.3 lm W-1 even at a high luminance of 5000 cd m-2 . The work unlocks the potential of TSF-OLEDs, paving the way toward practical applications.
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Affiliation(s)
- Dongdong Zhang
- Key Lab of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University, Beijing, 100084, China
| | - Xiaozeng Song
- Key Lab of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University, Beijing, 100084, China
| | - Minghan Cai
- Key Lab of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University, Beijing, 100084, China
| | - Lian Duan
- Key Lab of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University, Beijing, 100084, China
- Center for Flexible Electronics Technology, Tsinghua University, Beijing, 100084, P. R. China
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14
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Grieco C, Kennehan ER, Rimshaw A, Payne MM, Anthony JE, Asbury JB. Harnessing Molecular Vibrations to Probe Triplet Dynamics During Singlet Fission. J Phys Chem Lett 2017; 8:5700-5706. [PMID: 29112418 DOI: 10.1021/acs.jpclett.7b02434] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Ultrafast vibrational spectroscopy in the mid-infrared spectral range provides the opportunity to probe the dynamics of electronic states involved in all stages of the singlet fission reaction through their unique vibrational frequencies. This capability is demonstrated using a model singlet fission chromophore, 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-Pn). The alkyne groups of the TIPS side chains are coupled to the conjugated framework of the pentacene cores, enabling direct examination of the dynamics of triplet excitons that have successfully separated from correlated triplet pair states in crystalline films of TIPS-Pn. Relaxation processes during the separation of triplet excitons and triplet-triplet annihilation after their separation result in the formation of hot ground state molecules that also exhibit unique vibrational frequencies. Because all organic molecules possess native vibrational modes, ultrafast vibrational spectroscopy offers a new approach to examine the dynamics of electronic intermediates that may inform ongoing efforts to utilize singlet fission to overcome thermalization losses in photovoltaic applications.
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Affiliation(s)
- Christopher Grieco
- Department of Chemistry, The Pennsylvania State University , State College, Pennsylvania 16801, United States
| | - Eric R Kennehan
- Department of Chemistry, The Pennsylvania State University , State College, Pennsylvania 16801, United States
| | - Adam Rimshaw
- Department of Chemistry, The Pennsylvania State University , State College, Pennsylvania 16801, United States
| | - Marcia M Payne
- Department of Chemistry, University of Kentucky , Lexington, Kentucky 40506, United States
| | - John E Anthony
- Department of Chemistry, University of Kentucky , Lexington, Kentucky 40506, United States
| | - John B Asbury
- Department of Chemistry, The Pennsylvania State University , State College, Pennsylvania 16801, United States
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15
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Deng J, Jia W, Chen Y, Liu D, Hu Y, Xiong Z. Guest concentration, bias current, and temperature-dependent sign inversion of magneto-electroluminescence in thermally activated delayed fluorescence devices. Sci Rep 2017; 7:44396. [PMID: 28295056 PMCID: PMC5353579 DOI: 10.1038/srep44396] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2016] [Accepted: 02/07/2017] [Indexed: 11/18/2022] Open
Abstract
Non-emissive triplet excited states in devices that undergo thermally activated delayed fluorescence (TADF) can be up-converted to singlet excited states via reverse intersystem crossing (RISC), which leads to an enhanced electroluminescence efficiency. Exciton-based fluorescence devices always exhibit a positive magneto-electroluminescence (MEL) because intersystem crossing (ISC) can be suppressed effectively by an external magnetic field. Conversely, TADF devices should exhibit a negative MEL because RISC is suppressed by the external magnetic field. Intriguingly, we observed a positive MEL in TADF devices. Moreover, the sign of the MEL was either positive or negative, and depended on experimental conditions, including doping concentration, current density and temperature. The MEL observed from our TADF devices demonstrated that ISC in the host material and RISC in the guest material coexisted. These competing processes were affected by the experimental conditions, which led to the sign change of the MEL. This work gives important insight into the energy transfer processes and the evolution of excited states in TADF devices.
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Affiliation(s)
- Junquan Deng
- School of Physical Science and Technology, MOE Key Laboratory on Luminescence and Real-Time Analysis, Southwest University, Chongqing, 400715, P. R. China
| | - Weiyao Jia
- School of Physical Science and Technology, MOE Key Laboratory on Luminescence and Real-Time Analysis, Southwest University, Chongqing, 400715, P. R. China
| | - Yingbing Chen
- School of Physical Science and Technology, MOE Key Laboratory on Luminescence and Real-Time Analysis, Southwest University, Chongqing, 400715, P. R. China
| | - Dongyu Liu
- School of Physical Science and Technology, MOE Key Laboratory on Luminescence and Real-Time Analysis, Southwest University, Chongqing, 400715, P. R. China
| | - Yeqian Hu
- School of Physical Science and Technology, MOE Key Laboratory on Luminescence and Real-Time Analysis, Southwest University, Chongqing, 400715, P. R. China
| | - Zuhong Xiong
- School of Physical Science and Technology, MOE Key Laboratory on Luminescence and Real-Time Analysis, Southwest University, Chongqing, 400715, P. R. China
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16
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Grieco C, Doucette GS, Pensack RD, Payne MM, Rimshaw A, Scholes GD, Anthony JE, Asbury JB. Dynamic Exchange During Triplet Transport in Nanocrystalline TIPS-Pentacene Films. J Am Chem Soc 2016; 138:16069-16080. [DOI: 10.1021/jacs.6b10010] [Citation(s) in RCA: 67] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Christopher Grieco
- Department
of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Grayson S. Doucette
- Intercollege
Materials Science and Engineering Program, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Ryan D. Pensack
- Department
of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Marcia M. Payne
- Department
of Chemistry, University of Kentucky, Lexington, Kentucky 40506, United States
| | - Adam Rimshaw
- Department
of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Gregory D. Scholes
- Department
of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - John E. Anthony
- Department
of Chemistry, University of Kentucky, Lexington, Kentucky 40506, United States
| | - John B. Asbury
- Department
of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Intercollege
Materials Science and Engineering Program, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
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17
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Analysis of the phosphorescent dye concentration dependence of triplet-triplet annihilation in organic host-guest systems. Chem Phys Lett 2016. [DOI: 10.1016/j.cplett.2016.07.048] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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18
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Zhang L, van Eersel H, Bobbert P, Coehoorn R. Clarifying the mechanism of triplet–triplet annihilation in phosphorescent organic host–guest systems: A combined experimental and simulation study. Chem Phys Lett 2016. [DOI: 10.1016/j.cplett.2016.04.043] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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19
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Forrest SR. Excitons and the lifetime of organic semiconductor devices. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2015; 373:rsta.2014.0320. [PMID: 25987572 PMCID: PMC4455720 DOI: 10.1098/rsta.2014.0320] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
While excitons are responsible for the many beneficial optical properties of organic semiconductors, their non-radiative recombination within the material can result in material degradation due to the dumping of energy onto localized molecular bonds. This presents a challenge in developing strategies to exploit the benefits of excitons without negatively impacting the device operational stability. Here, we will briefly review the fundamental mechanisms leading to excitonic energy-driven device ageing in two example devices: blue emitting electrophosphorescent organic light emitting devices (PHOLEDs) and organic photovoltaic (OPV) cells. We describe strategies used to minimize or even eliminate this fundamental device degradation pathway.
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Affiliation(s)
- Stephen R Forrest
- Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI 48109, USA Department of Physics and Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109, USA
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