Photo- and electroactive amorphous molecular materials—molecular design, syntheses, reactions, properties, and applications

Shirota, Yasuhiko

doi:10.1039/b413819h

Cited by 909 publications

(541 citation statements)

References 169 publications

(266 reference statements)

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“…11͒ is too large to allow for CTC formation with F4-TCNQ. Both TDATA and CBP form amorphous films, 12 which rules out possible influences of film structure on our results. Therefore, the effects of acceptor diffusion on interface energetics could be studied in the presence ͑with TDATA͒ and absence ͑with CBP͒ of O/O CTCs.…”

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confidence: 98%

Interdiffusion of molecular acceptors through organic layers to metal substrates mimics doping-related energy level shifts

Duhm

Salzmann

Bröker

et al. 2009

Applied Physics Letters

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Photoemission measurements reveal energy level shifts toward the Fermi level when a strong electron acceptor ͑tetrafluoro-tetracyanoquinodimethane, F4-TCNQ͒ is deposited on pristine layers of 4,4Ј ,4Љ-tris͑N , N-diphenyl-amino͒triphenylamine ͑TDATA͒ or 4,4Ј-bis͑N-carbazolyl͒biphenyl ͑CBP͒. The shifts of the TDATA and CBP energy levels toward the Fermi level of the Au substrate could, in principle, arise from p-type doping of the intrinsic organic layers. While this indeed takes place in TDATA, doping of CBP by F4-TCNQ, i.e., charge transfer complex formation, does not occur. The shifts observed in CBP arise from the diffusion of F4-TCNQ toward the Au substrate, which modifies the buried metal surface potential, leading to a realignment of the energy levels of the organic overlayer. © 2009 American Institute of Physics. ͓DOI: 10.1063/1.3213547͔ Strong electron acceptor molecules are frequently used for electrical doping of hole transport layers in organic electronic devices. 1-4 They yield improved device performance due to organic/organic ͑O/O͒ charge transfer complex ͑CTC͒ formation in the codeposited thin films, which increases the layer conductivity and lowers the hole injection barrier ͑HIB; defined as energy difference between E F and the highest occupied molecular orbital onset͒ at the anode ͑p-type doping͒. Strong electron acceptors can also be used to precisely adjust the energy levels at organic/metal ͑O/M͒ interfaces, 5,6 even in the absence of doping. In this case, an O/M CTC ͑Ref. 7͒ is formed, which increases the effective substrate surface potential and thus reduces the HIB for any subsequently deposited organic material. 5,6 Note that HIB lowering due to O/M CTC formation may be misinterpreted as p-type doping of the organic layer ͑O/O CTC͒ because a shift of the donor energy levels toward the substrate Fermi level ͑E F ͒ occurs in both cases. Acceptors are often small molecules like tetrafluoro-tetracyanoquinodimethane ͑F4-TCNQ͒ ͓chemical structure shown in Fig. 1͑a͔͒, which can readily diffuse throughout crystalline organic layers; 8 furthermore, diffusion through amorphous organic layers may also occur, particularly when intermolecular interactions are weak. In such cases, the acceptor may reach the metal substrate ͓Fig. 1͑b͔͒ via diffusion and may form O/M CTCs. It may thus be difficult to identify the underlying mechanism that results in observed energy level shifts for organic donor/acceptor heterosystems, as O/M CTC formation may mimic p-type doping.To clarify the role of acceptor interdiffusion on the energy levels in organic heterosystems, we used ultraviolet photoelectron spectroscopy ͑UPS͒ to investigate the combination of F4-TCNQ with the donor 4,4Ј ,4Љ-tris͑N , N-diphenyl-amino͒triphenylamine ͑TDATA͒ and 4 , 4Ј-di͑N-carbazolyl͒biphenyl ͑CBP͒ ͓Fig. 1͑a͔͒, respectively, on Au substrates. While TDATA can be doped with F4-TCNQ, 9,10 the ionization energy of CBP with 6.3 eV ͑Ref. 11͒ is too large to allow for CTC formation with F4-TCNQ. Both TDATA and CBP form amorphous films, 12 which rul...

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confidence: 98%

Interdiffusion of molecular acceptors through organic layers to metal substrates mimics doping-related energy level shifts

Duhm

Salzmann

Bröker

et al. 2009

Applied Physics Letters

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“…[273] Triarylamines have been the subject of continuing research because of their optoelectronic properties. [274,275] Numerous methods have been disclosed for their synthesis by palladiumcatalyzed arylation of diarylamines. It has been demonstrated by Buchwald that under suitable conditions with dialkylbiaryl phosphine ligands it is possible to synthesize these molecules from anilines and an aryl chloride and an aryl bromide by exploiting the difference in reactivity of the two halides.…”

Section: Applications In Materials Sciencementioning

confidence: 99%

Biaryl Phosphane Ligands in Palladium‐Catalyzed Amination

2008

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Palladium-catalyzed amination of aryl halides has undergone rapid development in the last 12 years. This has been largely driven by implementation of new classes of ligands. Biaryl phosphines have proven to provide especially active catalysts in this context. This review discusses the applications that these catalysts have found in C-N cross-coupling in heterocycle synthesis, pharmaceuticals, materials science and natural product synthesis.

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“…The main classes of amorphous and thermally stable compounds are spiro [4], cardo [5], tetraphenylmethane based molecules [6] and star-burst [7] ones.…”

Section: Introductionmentioning

confidence: 99%

Star-burst 1H-pyrazolo[3,4-b]quinoline as chromophore for light-emitting diodes and photovoltaic devices

Gondek

Danel²,

Kityk

2010

Philosophical Magazine

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Photo- and electroactive amorphous molecular materials—molecular design, syntheses, reactions, properties, and applications

Cited by 909 publications

References 169 publications

Interdiffusion of molecular acceptors through organic layers to metal substrates mimics doping-related energy level shifts

Interdiffusion of molecular acceptors through organic layers to metal substrates mimics doping-related energy level shifts

Biaryl Phosphane Ligands in Palladium‐Catalyzed Amination

Star-burst 1H-pyrazolo[3,4-b]quinoline as chromophore for light-emitting diodes and photovoltaic devices

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