Simple hybrid dithiafulvenes-triphenylamine systems as dopant-free hole-transporting materials for efficient perovskite solar cells

Two extended hybrid conjugated systems based on a triphenylamine(TPA) core with two and three peripheral 1,4-dithiafulvenes(DTF) units coded WH-2 and WH-3 as hole-transporting materials(HTMs) applied in perovskite solar cells(PSCs) are synthesized by facile one-step reaction in good yield over 75%. DTF unit as electron donor can enhance the electron donating ability and the fusion of benzenic ring of TPA with DTF unit may lead to reinforced intermolecular interactions in the solid state. In addition,WH-2 and WH-3 exhibit a pyramid shape containing partial planarity and quasi three-dimensionality features, which is also conducive to enhancing the π-π stacking of molecules in the solid state. The above-mentioned structural characteristics make the two HTMs have good hole mobilities. As a result,WH-2 and WH-3 obtained the high intrinsic hole mobilities of 4.69 × 10^(-4)and 2.18 × 10^(-3)cm^(2)V^(-1)s^(-1)respectively. Finally, the power conversion efficiencies(PCEs) of PSCs with WH-2 and WH-3 as cost-effective dopant-free HTMs are 15.39% and 19.22% respectively and the PCE of PSC with WH-3 is on a par with that of PSC with Li-TFSI/t-BP doped Spiro-OMe TAD(19.67%).

Crystal Structure, One-and Two-photon Excited Fluorescence and Bioimaging of a D-π-A Structural Triphenylamine Derivative

An electron donor-π-bridge-electron acceptor(D-π-A) optical functional organic compound comprising a triphenylamine moiety as the electron donor and pyridine moiety as the electron acceptor was synthesized. The structure of the compound was solved by single-crystal X-ray diffraction analysis. It crystallizes in monoclinic, space group P21, with a = 9.753(5), b = 8.815(5), c = 25.554(5) ?, β = 96.315(5)°, V = 2184(2) ?~3, Z = 2, D_c = 1.136 g/m^3, F(000) = 792, Μr = 746.92, μ = 0.069 mm^(-1), the final R = 0.0658 and wR = 0.1730 for 6790 observed reflections with I > 2(I). Study of nonlinear optical properties shows that the compound exhibits excellent two-photon excited fluorescence with the two-photon absorption cross-section value of 116 GM. The structure-property relationship was researched in detail through X-ray crystallography and quantum chemical calculation. Result of living cell imaging experiment shows its potential in fluorescence microscopy bioimaging.

Synthesis and properties of a star-shaped organic material with triphenylamine and N-vinyl carbazole units

A starburst tripbenylamine cored N-vinyl carbazole （V-Cz） branched compound was designed and synthesized via optimized Heck reaction in a yield of 40-60%. Moderate yield came from decomposition of V-Cz and self-coupling of triiodo-triphenylamine. TCz-TPA adopts a highly twisted propeller conformation by molecular mechanical optimization. It is readily soluble for its highly twisted conformation. Transparent and pinhole free films could be easily fabricated by spin-coating for its starburst structure. It emits blue-greenish light in CH2Cl2 peaked at 460 nm with a narrow full-width at half-maximum （FWHM） of 65 nm. As compared,

Dopant-free small molecule hole transport materials based on triphenylamine derivatives for perovskite solar cells

In the past decade,perovskite solar cells have become a promising candidate in the photovoltaic industry owing to their high power conversion efficiency that surpasses 25%.However,there are certain limitations that have hindered the development and full-scale practical application of these cells,including the high cost and degradation of perovskite caused by the dopants.Hence,there is an urgent need to develop dopant-free hole transport materials(HTMs).In recent years,HTMs based on triphenylamine(TPA-HTMs)are receiving growing interest owing to their high hole mobility,excellent film formation,and suitable energy levels.The literature here covers work relevant to TPA-HTMs in the last five years.They have been classified according to different core types.The correlations between performance and structure are summarized,and the future development trend of TPA-HTMs is highlighted.

Synthesis and Properties of Novel Luminescent Compounds Containing Triphenylamine and Bipyridine Units

Blue luminescent compounds T1―T4 containing triphenylamine donors,bipyridine acceptors and olefinic linkers were synthesized and characterized by 1 H NMR,13 C NMR and high resolution mass spectrometry（HRMS）.Four compounds T1―T4 exhibit excellent solubility in common solvents and good film forming properties.Quantum chemical calculations show that compounds T1―T4 have asymmetric linear structures and the proper highest occupied molecular orbital（HOMO） levels.The UV-Vis absorption and fluorescence emission spectra of the four compounds in dilute chloroform solutions and on the solid films were measured.It reveals that compounds T1―T4 exhibit similar spectral behavior,suggesting that these compounds can form amorphous state in solid films.The calculated absorption and emission spectra of compounds T1―T4 are in good agreement with experimentally determined ones.Compounds T1―T4 have absolute fluorescence quantum yield above 17% in dilute chloroform solutions.Four compounds possess high glass-transition temperature（T g） exceeding 97 ℃ and the maximum T g is 155.28 ℃ for compound T3.Cyclic voltammetry measurements show that these compounds have proper HOMO levels in a range of-5.01―-5.13 eV for hole injection.The properties of compounds T1―T4 indicate that these compounds are candidates for the application in organic light-emitting devices（OLEDs） as hole-transporting materials（HTMs）.

Theoretical Study on Electronic, Optical, and Charge Transfer Properties of Starburst Triphenylamine as Sensibilizer @TiO2 Cluster for Dye-sensitized Solar Cells

Here, a series of starburst triphenylamine(WD8) derivatives for dye-sensitized solar cells(DSSCs) applications have been designed. The frontier molecular orbitals(FMOs) property, absorption spectra, and charge transfer rate property of WD8 and its derivatives were simulated. We also evaluated the FMOs energies and absorption spectra of WD8 and its derivatives with the TiO2 cluster. The simulation results show that the phenothiazine-triphenylamine and 2-cyanoacetic acid groups in the ortho-position will increase the HOMO energy, decrease the LUMO energy, and narrow the HOMO-LUMO gap of WD8. The charge injection from WD8 and its derivatives to TiO2 should be more favorable. The phenothiazine-triphenylamine and 2-cyanoacetic acid groups in the ortho-position will decrease the electron and hole injection barriers of WD8. The phenothiazinetriphenylamine and 2-cyanoacetic acid groups in the ortho-position will improve the absorption spectra properties of WD8. The absorption spectra of WD8 and its derivatives with the TiO2 cluster would have a red shift. The phenothiazine-triphenylamine and 2-cyanoacetic acid groups in the ortho-position will increase the charge transfer property of WD8.

Two-Photon Fluorescence Properties and Ultrafast Responses of a Hyperbranched Diketo-Pyrrolo-Pyrrole Polymer with Triphenylamine as the Core

The two-photon fluorescence properties and ultrafast responses of a hyperbranched polyyne （hb-DPP-J2） with triphenylamine as the central core, Diketo-Pyrrolo-Pyrrole as the connecting unit and electron acceptor are studied. The polymer has a D-π-A-π-D conjugated structure along the extended polyyne w-bridge systems, and the effective condugated unit repeats itself in the whole hyperbranehed polymer chain. The polymer exhibits a large two-photon absorption cross section and high fluorescence quantum yields. The ultrafast dynamic results give a deep understanding of the excited energy transfer processes under excitation, and reveal a long relaxation lifetime of the intramolecular charge transfer （ICT） state.

Synthesis and Properties of A Novel Triphenylamine Derivative

A novel triphenylamine derivative of 4, 4'-bis-[2-[4-[N, N-bis-(4-methoxyphenyl-amino)]phenyl-1-yl]-vinyl-1-yl]-1, 1'-biphenyl (DMPAVBI) was synthesized. The chemical structure wasconfirmed by IR, H NMR spectroscopy and elemental analysis. Its properties were studied by 1UV-Vis spectroscopy, photoluminescence spectroscopy and cyclic voltammetry methods.

Synthesis, Characterization and Properties of Bipolar Triphenylamine Charge Transport Materials

Four bipolar triphenylamine(TPA) charge transport materials were constructed by introducing imidazole and trifluoroacetyl groups into the TPA units, and characterized by the nuclear magnetic resonance spectrum(NMR) and mass spectrometry(MS). Among them, 4-(2-(1,3-trifluoroacetyl)imidazole)-phenyl-4,4?-di(4-methoxyphenyl)amine(2 Me OTPA-IOS, 1) was determined by X-ray single-crystal diffraction. The compound crystallizes in monoclinic system, space group P21/c with a = 24.338(5), b = 9.565(2), c = 11.456(2) ?, β = 99.427(3)°, Mr = 565.47, V = 2631.0(8) ?3,Z = 4,Dc = 1.428 g/cm3, μ = 0.125 mm–1, F(000) = 1160, the final R = 0.0559 and wR = 0.1265 for 5150 observed reflections with I > 2σ(I). The optimized configurations of the target compounds were obtained by quantum chemical calculation, and the bipolarity of transportable holes and electrons was predicted by the frontier molecular orbital(HOMO and LUMO), which was further confirmed by the time of flight(TOF) method. In addition, the introduction of the terminal flexible chain enhances the solubility, thermal stability(DSC and TGA) and film-forming property of all compounds, and the frontier orbital energy of the solid film of the compounds was also tested(UV-vis and PYS). Thus, these compounds have the bipolarity of transportable holes and electrons and show good solubility and thermal stability.

Triphenylamine-based highly active two-photon absorbing chromophores with push-pull systems

Two triphenylamine-based star-type push-pull chromophores(T1, T2) were designed and synthesized.Triphenylamine serves as the central core and acts as an electron-donating group surrounded by electronwithdrawing pentafluorobenzene or N,N-dimethyl substituted tetrafluorobenzene, which are connected by ethylene bridges. Single-crystal X-ray diffraction confirmed the structures and molecular arrangement of two chromophores. The systematic photophysical research of T1 and T2 absorption characteristics was carried out to gain a better understanding of how structure-property relationships affect the observed nonlinear optical absorption phenomenon. Complementary calculations based on density functional theory(DFT) further confirmed the experimental results. Both chromophores exhibited excellent two-photon absorption(TPA) properties in CH_(2)Cl_(2). Notably, T2 has more remarkable nonlinear optical absorption effects with the TPA cross-section up to 4.24 × 10~7GM. By adjusting the electronic structures of the chromophores through introducing pentafluorobenzene or N,N-dimethyl as functional groups with different electron-donating or withdrawing behaviors, the TPA performance of the small organic molecule could be greatly enhanced. These molecular structures with push-pull systems were excellent candidates for different two-photon applications.

Synthesis and Electrochromic Properties of Polyimides with Pendent Benzimidazole and Triphenylamine Units

Five novel near-infrared electrochromic aromatic polyimides （PIs） with pendent benzimidazole group were synthesized from 4,4＇-diamino-4＂-（1-benzylbenzimidazol-2-yl）triphenylamine （named as DBBT） with five different dianhydrides via two-step polymerization process, respectively. The maximum UV-Vis absorption bands of these PIs locate at about 335 nm for solid films due to the π-π＊ transitions. A reversible pair of distinct redox peaks, that were associated with a noticeable color change from original yellow to blue, was observed in the cyclic voltammetry （CV） test. A new absorption peak emerged at 847 nm in near-infrared （NIR） region with increasing voltage in UV-Vis-NIR spectrum, which indicates that PI can be used as NIR electrochromic material. These novel PIs have good electrochemical stability, appropriate energy levels for the highest occupied molecular orbital （HOMO） and the lowest unoccupied molecular orbital （LUMO）, in the range of-5.17 eV to -5.20 eV and -2.14 eV to -2.26 eV （versus the vacuum level） determined by cyclic voltammetry method. These values basically consisted with the results of quantum chemical calculation. These polyimides can be used as novel electrochromic and hole transportation materials.

Novel Organic Dyes Based on Bulky Tri（triphenylamine）-Substituted Styrene for Dye-Sensitized Solar Cells

Three novel donor-n-acceptor （D-π-A） metal-free organic dyes （TB, TS and TF） based on tri（triphenylamine）- substituted styrene as donor with various conjugated linkers （benzene, thiophene and furan） were synthesized, characterized and used for the application of dye-sensitized solar cells （DSSCs）. Under the same condition, The photo-to-electrical conversion efficiency of the DSSCs sensitized with TB, TS and TF reach 1.84%, 4.10% and 4.52%, respectively, which are lower than that sensitized with RI （5.02%） with one triphenylamine unit. The results suggest that these bulky donor-based sensitizers are unfavorable to DSSCs.

A Bulky Pyridinylfluorene/Triphenylamine Hybrid Used as Host Material for Heavily-Doped Blue Electrophosphorescent Devices

In this work, a novel molecule pyridinylfluorene/triphenylamine hybrid （TPyFTPA） with bulky steric hindrance effects has been synthesized successfully by substituting 9-（pyridine-2-yl）-fluoren-9-yl with triphenylamine （TPA） via Friedel-Crafts reaction, which possesses good thermal stability and triplet energy （ET） of 420 ℃ with 5% weight loss and 2.86 eV, respectively. Moreover, the bulky steric hindrance material shows high stable morphology by heating to 200 ℃ without finding melting phenomena and crystallization that is demonstrated by differential scanning calorimetry （DSC） curve. The bulky pyridinylfluorene end-capped TPA has been used as host material for blue phosphorescent organic light-emitting diodes （PhOLEDs） with maximum external quantum efficiencies （EQEs） of 2.7%, 3.7%, and 3.5%, at the doping ratios of 10%, 30%, and 40%, respectively. The performances of TPyFTPA-based blue PhOLEDs own wide concentration ranging from 10% to 40%, which indicates the bulky TPyFTPA might be a potential candidate for inexpensive products with simplifying process for the applications in full-color display and solid state lighting.

Acid-induced tunable white light emission based on triphenylamine derivatives

A series of triphe nylamine(TPA)derivatives with various substituent groups were prepared and showed different absorption and fluorescence characteristics due to the substituent effect.On account of the existence of pyridine units,these TPA derivatives exhibited acid-induced tunable multicolor fluorescence emission including white light emission.In addition,acid-induced fluorescence regulation of these compounds has been also realized in the solid state,which enable them to be successfully constructed the stimuli-responsive fluorescent films and fluorescent inks for inkjet printing.

New Organic Dyes Based on Biarylmethylene-Bridged Triphenylamine for Dye Sensitized Solar Cell

Three new organic dyes were synthesized and characterized for applications in dye-sensitized solar cells （DSSCs）. In these dyes, diarylmethylene-bridged triphenylarnine is the donor, and different acceptors and vinyl- thiophene are designed to get TBA-1, TBA-2 and TBA-3. Their photophysical, electrochemical and photovoltaic properties were investigated, and the effects of the acceptor structures as well as the linkage on these properties were evaluated. Results demonstrated that the vinylthiophene linkage between the donor and the acceptor is favor- able for improving light harvesting ability of TBA-2. In addition, the electrochemical impedance spectroscopy ex- periments suggest larger Rrec and longer electron lifetime of TBA-2. Therefore, it outperforms the other dyes, exhib- iting the highest power conversion efficiency of 3.87%, with Jsc of 8.25 mAocm-2 and Voc of 666 mV. Unfortunately, the TBA-3 with three acceptor groups only shows efficiency of 3.52%, indicating that the design of increasing ac- ceptor groups plays little role on enhancing the solar cell efficiency.

Novel Small Four-armed Molecules with Triphenylamine-bridged Structure for Organic Solar Cells Featuring High Open-circuit Voltage

In view of few attention on star-shaped molecules containing triphenylamine(TPA)unit asπ-linker,a series of small four-armed molecules,consisting of octyloxy-substituted 2,1,3-benzothiadiazole(DOBT)or 4-octyl-2-thienyl functionalized DOBT as the core,TPA asπ-bridge and 4-methylphenyl or 4-methoxyphenyl groups as terminal units,was designed and synthesized.The effects ofπbridges and substitute groups on molecular photoe-lectric performance and photovoltaic performance were fully explored.With the help of the additional thiophene-linkers incorporation,3-octylthienyl substituted molecule with end-capping 4-methylphenyl(T-BTTPAM)and 3-octylthienyl substituted molecule with end-capping 4-methoxyphenyl(T-BTTPAOM)showed stronger and broader absorption,as well as higher charge mobilities compared to the molecules without thiophene-linkers(BTTPAM and BTTPAOM).Additionally,changing substitute groups from methyl to methoxy helped BTTPAOM and T-BTTPAOM achieve better absorption properties than BTTPAM and T-BTTPAM,respectively.When paired with PC61BM as the electron acceptor to fabricate solution-processed photovoltaic devices,the four materials gave high open-circuit voltage(Voc)values over 0.90 V.These results demonstrate that our materials are promising candidates as donor materials for organic solar cells(OSCs),and further device optimization is in progress in our laboratory.

PHOTOPHYSICAL STUDIES ON ORGANIC COMPOUNDS——TIME-RESOLVED TRANSIENT ABSORPTION SPECTRA STUDIES ON TRIPHENYLAMINE IN VARIOUS SOLVENTS

The transient absorption spectra of triphenylamine (TPA) in various solvents have beeninvestigated by the methods of nanosecond laser photolysis. The lifetimes of TPA were meas-ured. In hexane and ethanol, the transient absorptions of triplet state and triplet excimer ofTPA were observed. However, the transient absorptions of the TPA cation radical was alsoobserved in acetonitrile besides that of the triplet TPA monomer and excimer. According tothe experimental facts, the transient photophysical mechanism of TPA in various solvents hasbeen proposed.

Study of third-order nonlinear susceptibility of polySchiff base containing triphenylamine

PolySchiff base containing triphenylamine has been synthesized by polycondensation and character-ized by FT-IR,NMR,UV-visible spectrometer. Measurements of the third-order optical nonlinear sus-ceptibility χ(3) by Z-scan technique have shown that the large nonlinearity is dominated by the two-photon absorption in PSB. The sign and size of real part Reχ(3) ,nonlinear refractive index n2 have been measured with the condition of 532 nm,8 ns-duration pulses to be -1.23×10-10 esu,-3.06×10-12 esu;nonlinear absorption index β and size of image part Imχ(3) to be 3.63×10-10 m/W,1.15×10-11 esu,respec-tively,so the third-order nonlinear susceptibility χ(3) is 1.19×10-11 esu. The value is larger than other polymers reported. PSB is self-focusing material and has potential application in nonlinear optic field.

Triphenylamines consisting of bulky 3,5-di–tert–butyl–4-anisyl group:Synthesis, redox properties and their radical cation species

Triphenylamine(TPA) derivatives have been widely used as useful building blocks for diverse functional materials because of their excellent redox activity. Most of the molecular structures of TPA-based organic functional materials contain 4-anisyl groups, which on one hand could reduce their oxidation potential and on the other hand significantly delocalize the spin density of the resultant TPA radical cation species and enhance their stability. However, molecular-level investigation of the redox behavior of triphenylamines consisting of 4-anisyl group and the electronic structures of their radical cation species has not been reported in the literature. Herein, we design a series of triphenylamines consisting of one, two, or three 3,5-di–tert–butyl–4-anisyl groups and investigate their redox behaviors and corresponding radical cation species. We disclose that the resonance hybrid and steric protection could both contribute to the stability of triphenylamine radical cations. Moreover, further oxidation leads to an unexpected oxidative demethylation. The findings in this work may reveal new insights for the understanding of the unique redox properties of 4-anisyl substituted triphenylamines.