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Abstract: Four novel blue luminescent hole transporting materials with N,N′-di(p-tolyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine as the core, containing triphenylamine units and olefinic linkers were synthesized and characterized by FT-IR, 1H NMR and HRMS. Their optical, electrochemical and thermal properties were investigated. Quantum-chemical calculations were performed to obtain their optimized structures and the electron distribution of the molecular orbital energy levels, and the experimental findings suggest that monosubstituted compounds have a similar energy gap to the bisubstituted compounds. The UV–Vis and photoluminescence spectra indicate that these compounds are blue luminescent materials. Cyclic voltammetry measurements show that the four compounds embody suitable highest occupied molecular orbital levels (in a range of −5.08 ∼ −5.14 eV) for hole injection. All of the compounds have excellent thermal stability, with decomposition temperatures above 400 °C and glass transition temperatures above 100 °C, which is of benefit to form stable amorphous glassy states. [Copyright &y& Elsevier]

Abstract: Two new blue luminescent hole transporting materials (HTM) containing triphenylamine, carbazole units and olefinic linkers (TM1 and TM2) were synthesized via Wittig reaction and characterized by 1H NMR, FT-IR, and HRMS. The compounds show good solubility in common organic solvents such as dichloromethane, chloroform, tetrahydrofuran and dimethyl formamide. Their optical, electrochemical and crystalline properties were investigated by using UV–Vis, photoluminescence (PL) spectra, cyclic voltammetry (CV) and differential scanning calorimetry (DSC), respectively. Quantum-chemical calculation was performed to obtain their optimized structures and the electron distribution of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels. The UV–Vis absorption and PL spectra of the two compounds in solid state were found to be similar to that when they were in dilute THF, which suggests that these compounds remain as an amorphous state in solid films. CV measurements show that the two compounds embody suitable HOMO levels (in a range of −5.28 to −5.23eV) for hole injection, which is consistent with the calculation consequence. Two compounds possess high glass-transition temperature (Tg ) at 96.61 and 90.74°C for TM1 and TM2, respectively, suggesting the two compounds could form stable amorphous glassy states. The experimental results show that the synthesized compounds have great potential for application in organic light-emitting devices (OLEDs). [Copyright &y& Elsevier]

• The new materials of T-6TPA with high hole mobility of 2.06 × 10−3 cm2V−1s−1 was synthesized for dopant‐free HTL. • The infiltration strategies can further improve the interface hole extraction and transport between HTL and perovskite. • Anti-solvent drip strategy can construct a more effective charge transport channel in the perovskite. • The PCE of PSC with dopant-free T-6TPA HTL has increased from 18.5% to 20.3% with the assistance of antisolvent dripping. • The PSCs with T-6TPA dopant-free HTL presents good long-term stability in both humid air and high temperature of 60 °C. Perovskite solar cells (PSCs) with dopant‐free hole transporting layers (HTLs) deserved extensive research by merits of their outstanding hydrophobicity and stability. However, the low carrier mobility and poor interfacial hole extraction lead to the inferior power conversion efficiency (PCE) than that of conventional Li+ doped Spiro-OMeTAD. Here, a design of triphenylamine groups grafted triphenylene derivative (T-6TPA) as dopant-free HTLs has been presented. The larger π-conjugation in T-6TPA give rise to high hole mobility of 2.06 × 10−3 cm2V−1s−1. Moreover, the interfacial hole extraction of T-6TPA was significantly promoted when the molecules were infiltrated into perovskite before HTL deposition. The infiltration method of anti-solvent dripping (An) strategy increased PCE from 18.5% up to 20.3%, which is superior to another additive doping strategy (Ad-strategy, 19.3%). The effectiveness of An-strategy can be attributed to the construction of a coherent and homogeneous hole transport channel. The hydrophobicity and high glass transition temperature of T-6TPA also granted excellent moisture and thermal stabilities that the initial PCE could remain 80% for 60 days in air or 600 h at 60 °C. This work highlights the synergistical optimization by design of highly hole-mobile materials as well as the interfacial network construction for charge transport. [ABSTRACT FROM AUTHOR]

Five donor-acceptor anthraquinone dyes based on phenylamine/triphenylamines with different substituted groups were synthesized by Suzuki reaction in good yields, and the photophysical properties were studied in organic solvents with different polarity. The title dyes exhibited remarkable solvatochromic fluorescence (>190 nm emission shift in polar media), which was derived from intramolecular charge transfer (ICT) character that revealed by DFT/TD-DFT calculation. And large Stokes shifts (210–306 nm) were observed in different organic solvents, along with rich color changes from blue to green, yellow, orange and even purple-red. The Stokes shifts were linearly dependent on the solvent polarity function E T (30). Interestingly, it was found from the single-crystal X-ray diffraction analysis that dye 3 displayed two different interleaved channel structures, which was seldom seen in organic compounds and could be used as host for complexation potentially. Electrochemical characterization suggested that the different substituted phenylamine groups attached to anthraquinone unit could lead to tunable potentials and energy levels. [ABSTRACT FROM AUTHOR]

Two star-shaped TPA-based small-molecule materials (Z1012 and Z1013) were designed and synthesized in this paper. These molecules show high hole mobility and suitable energy levels for CH 3 NH 3 PbI 3 -based perovskite solar cells. Photovoltaic cells based on the Z1013 without any dopants or additives achieve an excellent power conversion efficiency (PCE) of 15.4%, which is comparable to devices based on state-of-art p-doped spiro -OMeTAD. Moreover, the devices based on these two HTMs show much better stability than that of devices based on spiro -OMeTAD when aging in ambient air both at room temperature and 80 °C. These results demonstrate that star-shape TPAs could be excellent dopant-free HTMs for perovskite solar cells and hold promise to replace the p-doped spiro -OMeTAD, which is important for the fabrication of cost-effective and stable devices. [ABSTRACT FROM AUTHOR]

Three small molecular hole-transporting and emitting materials with naphthalene bridged triphenylamine or carbazole were synthesized. These compounds exhibited high absolute fluorescence quantum yields (70–88%) at the green light region (540–555 nm), suitable highest occupied molecular orbital levels (−5.26 ∼ −5.34 eV) and good hole mobilities (∼10 −4 cm 2 V −1 s −1 ). The hole-only organic light emitting diodes with as-synthesized hole-transporting and emitting materials showed a tune-on voltage and a maximum brightness of 2.6 V and 2010 cd m −2 , respectively. Three stages of voltage-dependent current were observed, which coincide with the characteristic of Ohmic current, Fowler-Nordheim current and space charge limited current. With analysis of above models, overlarge Fowler-Nordheim current and space charge limited current contribute to the low efficiency of the device. All these results indicated that the high hole mobility showed the negative effect on the device efficiency, especially at high operation voltage. [ABSTRACT FROM AUTHOR]

A triphENylamine based molecular “butterfly” is developed as dopant ‐ free hole ‐ transport material for perovskite solar cells exhibiting excellENt power conversion efficiENcy of 16.3% which is comparable to the state ‐ of ‐ the ‐ art doped 2,2′,7,7′ ‐ tetrakis(N,N′ ‐ di ‐ p ‐ methoxy ‐ phENylamine) ‐ 9,9′ ‐ spirobifluorENe (spiro ‐ OMeTAD). Moreover, the device is much more stable than that of spiro ‐ OMeTAD based device under light irradiation. [ABSTRACT FROM AUTHOR]

Film-forming property of organic semiconductors is one of crucial factors for the performance of flexible organic light-emitting diode. In this work, two hole transporting materials based on triphenylamine were synthesized, which showed an outstanding film-forming property and could form free-standing films with a diameter of 4 mm. The spin-coated films on the flexible substrates showed an unobvious mechanical failure bended with radius of curvature no less than 6 mm. Photoelectron yield spectroscopy show that the two compounds embody suitable highest occupied molecular orbital levels (−5.14 eV and −5.25 eV) for hole injection. The sandwiched organic light-emitting diodes use poly[2-(4-3′,7′-dimethyloctyloxy)-phenyl]- p -phenylenevinylene) as emitting and electron transporting layer showed higher stability with increasing operation current density, an maximum luminance level of 103,690 cd m −2 . It demonstrate that the as-synthesized hole transporting materials hold a promising in high brightness flexible organic light-emitting diodes. [ABSTRACT FROM AUTHOR]

We report two simple triphenylamine-based hole-transporting materials (HTMs) containing vinyl derivatives, 3,6-di(2-(4-(N,N-di(p-tolyl)amino)phenyl)vinyl)-2-thiophene (apv-T) and 3,6-di(2-(4-(N,N-di(p-tolyl)amino)phenyl)vinyl)-9-ethyl-carbazole (apv-EC) for the perovskite solar cells. According to theoretical calculation and experimental results, their HOMO energy levels are similar to that of conventional spiro -OMeTAD, which is supposed to be favorable for the hole transportation in the device. Up to 12% of light-to-electricity conversion efficiency has been achieved for the mesoporous TiO 2 /CH 3 NH 3 PbI 3 /apv-EC/Au solar cell without using p -type dopants. Time-resolved photoluminescence (PL) measurement and Electrochemical Impedance Spectra (EIS) further reveal that relatively high hole mobility of the apv-EC and weak recombination occurred at TiO 2 /CH 3 NH 3 PbI 3 /apv-EC interfaces of the device are crucial to the good performance in comparison with the apv-T. Advantages such as easy synthesis, low cost and relatively good cell performance provide a potential application as the replacement of the expensive spiro -OMeTAD. [ABSTRACT FROM AUTHOR]

Abstract: A series of novel electrochromic chalcones containing triphenylamine units were synthesized by Aldol reaction and characterized by NMR, IR and MS. Their optical, electrochemical properties were investigated using UV–vis, photoluminescence spectra and cyclic voltammetry. The molecular orbital energy levels and excitation energies were calculated by quantum chemical calculation. It was found that the fluorescence intensity is decreasing with formation of charge-transfer state. The existence of electron donating group on triphenylamine unites caused a significant bathochromic shift of the UV absorption maximum and increased E HOMO and E LUMO. The electrochromic property of the synthesized compounds was studied by spectroelectrochemical experiments. The results showed that the chalcones containing triphenylamine moiety presented good electrochromic stability, with a color change from yellow to blue as applied potentials ranging from 0.0 to 2.8 V. The coloring and bleaching time was in the range of 2.9–4.2 s and 1.7–3.3 s, respectively. [Copyright &y& Elsevier]

Regulating hole injection via self-assembled monolayers (SAMs) modification on indium tin oxide (ITO) is significantly favourable for achieving high efficiency and stability of organic light-emitting diodes (OLEDs). In this work, ITO was modified by pentafluorobenzylphosphonic acid (F 5 B n PA) and heneicosafluorododecylphosphonic acid (HF 21 DPA) in a binary SAMs way. By altering mole ratios of these two materials, ITO work function can be achieved from 5.20 to 5.82 eV and the roles of F 5 B n PA and HF 21 DPA in affecting hole injection and device performances were also explored. The results demonstrate a synergistic effect that HF 21 DPA improves ITO work function efficiently for its fluorinated alkyl chain and F 5 B n PA enhances the charge transfer directly due to its aromatic group gathering HOMO level. When α-naphthylphenylbiphenyldiamine (NPB) and 4,4′,4″-tris(carbazol-9-yl) triphenylamine (TCTA) were used as hole transport layers (HTLs) in OLEDs with a structure of ITO/SAM/HTL/tris(8-hydroxyquinolino) aluminum (III) (Alq 3)/lithium fluoride (LiF)/Al, brightness up to 36839 and 58189 cd/m2 and current efficiency up to 5.75 and 7.35 cd/A were obtained, respectively. Furthermore, the influence of binary SAMs on the stability of NPB-based OLEDs was studied. The maximum half-lifetime at the initial brightness of 2200 cd/m2 reaches 368.0 h, which is 75.1 times that of the poly(3, 4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)-containing device. The high durability is attributed to higher hydrophobicity and lower hole injection barrier caused by SAMs. This is the first report on the synergistic effect of aromatic and aliphatic compounds in binary SAMs on regulating hole injection, showing a new approach of obtaining high efficiency and stability of OLEDs. Image 1 • The synergistic effect of aromatic and aliphatic compounds on ITO properties and OLED performances was firstly reported. • The modified OLEDs based on different HTLs showed preferable performances by varying composition of binary SAMs. • Moreover, an excellent stability was presented when applying these binary SAMs to modify OLEDs with a simplified structure. [ABSTRACT FROM AUTHOR]