Investigation of Organic-Organic Interfaces by Time-Resolved Photocurrent, Electrochemical, And Photoemission Techniques

1997 ◽  
Vol 488 ◽  
Author(s):  
Liang-Bih Lin ◽  
M. Gary Mason ◽  
Ralph H. Young ◽  
Deniz E. Schildkraut ◽  
Paul M. Borsenberger ◽  
...  
Keyword(s):  
Hole Transport ◽  
Hole Injection ◽  
Photoemission Spectroscopy ◽  
Energy Barriers ◽  
Time Resolved ◽  
Transient Photocurrent ◽  
Oxidation Potentials ◽  
Organic Interfaces ◽  
Hole Transporting ◽  
Organic Electroluminescent

AbstractHole transporting properties and energy barriers at organic-organic interfaces relevant to electrophotographic and organic electroluminescent (EL) devices are described. Three wellknown hole transporting molecules, 1,1-bis(di-4-tolylaminophenyl)cyclohexane (TAPC), N,N′- diphenyl-N,N′-bis(1 -naphthyl)-(1,1 ′-biphenyl)-4,4′-diamine (NPB), and N,N,N′,N′-tetrakis(4- tolyl)-(1,1 ′-biphenyl)-4,4′-diamine (TTB) are used in this study. The ionization potentials (IP) and oxidation potentials (Eox) of these materials are determined by photoemission spectroscopy and electrochemical measurements, from which a conversion formula is obtained (IP ∼ 4.5 eV + eEox). Hole transport across organic-organic interfaces is investigated by time-of-flight transient photocurrent techniques. The efficiencies of hole injection are consistent with the energy barriers, when present, at these interfaces.

Synthesis, thermal, electrochemical, and photophysical characterization of 1,5-bis(diarylamino)naphthalene derivatives as potential hole transport OLED materials

2005 ◽  
Vol 83 (6-7) ◽  
pp. 958-968 ◽  
Author(s):  
Jingning Shan ◽  
Glenn PA Yap ◽  
Darrin S Richeson
Keyword(s):  
Photophysical Properties ◽  
Energy Levels ◽  
Hole Transport ◽  
Similar Degree ◽  
Naphthalene Derivatives ◽  
Emission Data ◽  
Oxidation Potentials ◽  
Hole Transporting ◽  
Palladium Catalyzed ◽  
The Difference

Novel 1,5-bis(diarylamino)naphthalene derivatives (1–9), which have potential as hole-transporting materials for electroluminescent devices, were obtained through palladium-catalyzed coupling of diarylamines and 1,5-dibromonaphthalene. The thermal, electrochemical, and photophysical properties of these compounds were examined and the effects of the N-aryl substituents on these properties were investigated. These materials possess glass transition temperatures (Tg) that range from 70–131 °C and these values are related to the identity of the aryl substituents. Cyclic voltammetric measurements demonstrated that these compounds possess two reversible oxidation processes and were further used to estimate the HOMO energy levels of these materials by comparison with the ferrocene/ferrocenium couple. The intramolecular charge mobility, as gauged by the difference between the two oxidation potentials, indicates that compounds 1–8 have a similar degree of delocalization as meta-diaminobenzene derivatives while that of 9 is similar to TPD. Compounds 1–9 emit in the blue-green region and optical absorption and emission data for these materials can be rationalized in terms of the electronic donating properties of the aryl substituents. This data when combined with the electrochemically determined HOMO energies allowed estimation of the LUMO energy levels.Key words: hole transport materials, diaminonaphthalene, thermal analysis, palladium-catalyzed arylation.

Theoretical Investigation of Organic Amines as Hole Transporting Materials: Correlation to the Hammett Parameter of the Substituent, Ionization Potential, and Reorganization Energy Level

2009 ◽  
Vol 62 (5) ◽  
pp. 483 ◽  
Author(s):  
Jiunn-Hung Pan ◽  
Yu-Ma Chou ◽  
Houn-Lin Chiu ◽  
Bo-Cheng Wang
Keyword(s):  
Radical Cation ◽  
Density Functional ◽  
Reorganization Energy ◽  
Hole Transport ◽  
Substitution Effects ◽  
Oxidation Potentials ◽  
Hole Transporting ◽  
Organic Amines ◽  
Hammett Parameter ◽  
Hole Transporting Materials

Theoretical calculations on organic amines widely used as hole-transporting materials (HTMs) in multilayer organic light-emitting diodes have been performed. The calculated Ip and the reorganization energy for hole transport (λ+) of triphenylamine (TPA), 9-phenyl-9H-carbazole (PC), and their derivatives, are found to be related to their Hammett parameter (σ). In this study, the density functional theory (DFT) calculation is used to optimize 82 TPA and PC derivatives. Electronic structures of these compounds in the neutral and the radical-cation states are obtained based on calculations on optimized geometrical structures. The Ip and λ+ values are derived from calculated heats of formation (or total energy) of the neutral and the radical-cation states. In particular, the calculated Ips for these derivatives correlate well with the experimental data. The substitution effect for the mono-substituted TPA and PC is displayed in that the Ips of the TPA and PC derivatives with electron-donating and -withdrawing substituents are lower and higher than those of TPA and PC, respectively. For the effect of substitution position, the para-substituted TPA derivatives have higher Ip and –EHOMO than those of meta-substituted TPAs. The substitution effects in di- and tri-substituted TPAs are more pronounced than that of mono-substituted ones. According to the results, the calculated Ips shows an excellent agreement with the experimental oxidation potentials (EP/2) in these TPA derivatives. Furthermore, these calculation results can be employed to predict electro-luminescent properties for new and improved HTMs.

Controlled Injection of Holes into ALQ3 Based Oleds by Means of An Oxidized Transport Layer

2001 ◽  
Vol 708 ◽  
Author(s):  
Mathew K. Mathai ◽  
Keith A. Higginson ◽  
Bing R. Hsieh ◽  
Fotios Papadimitrakopoulos
Keyword(s):  
Indium Tin Oxide ◽  
Oxidative Degradation ◽  
Transport Layer ◽  
Hole Injection ◽  
Carrier Injection ◽  
Salt Loading ◽  
Light Emitting ◽  
Hole Transporting ◽  
Intrinsic Degradation ◽  
Variable Conductivity

ABSTRACTIn this paper we report a method for tuning the extent of hole injection into the active light emitting tris- (8-hydroxyquinoline) aluminum (Alq3) layer in organic light emitting diodes (OLEDs). This is made possible by modifying the indium tin oxide (ITO) anode with an oxidized transport layer (OTL) comprising a hole transporting polycarbonate of N,N'-bis(3-hydroxymethyl)-N,N'-bis(phenyl) benzidine and diethylene glycol (PC-TPB-DEG) doped with varying concentrations of antimonium hexafluoride salt of N,N,N',N'-tetra-p-tolyl-4,4'-biphenyldiamine (TMTPD+ SbF6-). The conductivity of the OTL can be changed over three orders of magnitude depending on salt loading. The analysis of hole and electron current variations in these devices indicates that optimizing the conductivity of the OTL enables the modulation of hole injection into the Alq3 layer. The bipolar charge transport properties for OLEDs in which the interfacial carrier injection barriers have been minimized, are governed by the conductivities of the respective layers and in this case it is shown that the variable conductivity of the OTL does allow for better control of the same. Accordingly, varying the concentration of holes in the device indicates that beyond an optimum concentration of holes, further hole injection results in the formation of light quenching cationic species and the initiation of oxidative degradation processes in the Alq3 layer, thus accelerating the intrinsic degradation of these devices. The variable conductivity of the OTL can hence be used to minimize the occurrence of these processes.

scholarly journals Effects of 5-Ammonium Valeric Acid Iodide as Additive on Methyl Ammonium Lead Iodide Perovskite Solar Cells

Nanomaterials ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 2512
Author(s):  
Daming Zheng ◽  
Changheng Tong ◽  
Tao Zhu ◽  
Yaoguang Rong ◽  
Thierry Pauporté
Keyword(s):  
Solar Cells ◽  
Perovskite Solar Cells ◽  
Single Crystal Silicon ◽  
Mesoporous Structure ◽  
Valeric Acid ◽  
Electrical Impedance Spectroscopy ◽  
Lead Iodide ◽  
Crystal Silicon ◽  
Time Resolved ◽  
Hole Transporting

During the past decade, the power conversion efficiency (PCE) of perovskite solar cells (PSCs) has risen rapidly, and it now approaches the record for single crystal silicon solar cells. However, these devices still suffer from a problem of stability. To improve PSC stability, two approaches have been notably developed: the use of additives and/or post-treatments that can strengthen perovskite structures and the use of a nontypical architecture where three mesoporous layers, including a porous carbon backcontact without hole transporting layer, are employed. This paper focuses on 5-ammonium valeric acid iodide (5-AVAI or AVA) as an additive in methylammonium lead iodide (MAPI). By combining scanning electron microscopy (SEM), X-ray diffraction (XRD), time-resolved photoluminescence (TRPL), current–voltage measurements, ideality factor determination, and in-depth electrical impedance spectroscopy (EIS) investigations on various layers stacks structures, we discriminated the effects of a mesoscopic scaffold and an AVA additive. The AVA additive was found to decrease the bulk defects in perovskite (PVK) and boost the PVK resistance to moisture. The triple mesoporous structure was detrimental for the defects, but it improved the stability against humidity. On standard architecture, the PCE is 16.9% with the AVA additive instead of 18.1% for the control. A high stability of TiO2/ZrO2/carbon/perovskite cells was found due to both AVA and the protection by the all-inorganic scaffold. These cells achieved a PCE of 14.4% in the present work.

A polymeric bis(di-p-anisylamino)fluorene hole-transport material for stable n-i-p perovskite solar cells

2021 ◽  
Author(s):  
Marie-Hélène Tremblay ◽  
Kelly Schutt ◽  
Yadong Zhang ◽  
Stephen Barlow ◽  
Henry J. Snaith ◽  
...  
Keyword(s):  
Solar Cells ◽  
Perovskite Solar Cells ◽  
Heat Stability ◽  
Hole Transport ◽  
Side Chains ◽  
Hole Transporting

Half-devices made with a norbornene homopolymer with hole-transporting 2,7-bis(di-p-anisylamino)fluorene side chains exhibit improved light and heat stability in comparison to those incorporating spiro-OMeTAD.

scholarly journals Step-saving synthesis of star-shaped hole-transporting materials with carbazole or phenothiazine cores via optimized C–H/C–Br coupling reactions

RSC Advances ◽  
2021 ◽  
Vol 11 (15) ◽  
pp. 8879-8885
Author(s):  
Jui-Heng Chen ◽  
Kun-Mu Lee ◽  
Chang-Chieh Ting ◽  
Ching-Yuan Liu
Keyword(s):  
Solar Cell ◽  
Perovskite Solar Cell ◽  
Hole Transport ◽  
Coupling Reactions ◽  
Hole Transporting ◽  
Shaped Hole ◽  
Hole Transporting Materials

Carbazole or phenothiazine core-based hole-transport materials are facilely accessed by an optimized synthesis-shortcut. Perovskite solar cell devices with 6–13 demonstrate PCEs of up to 17.57%.

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