Symmetrical and unsymmetrical azomethines with thiophene core : structure - properties investigations

Unsymmetrical and symmetrical azomethines were obtained using the condensation reaction of diamino-thiophene-3,4 dicarboxylic acid diethyl ester with 4-(1-pyrrolidino)benzaldehyde, fluorene-2-carboxaldehyde, 1-methylindole-3-carboxaldehyde, and benzothiazole-2-carboxaldehyde. Their thermal, optical, and electrochemical properties were investigated, and the results were supported by calculations using the density functional theory. The studied compounds melted in the range of 170–260 °C and can be converted into amorphous materials with high glass transition temperatures between 76 and 135 °C. They were thermally stable up to 220–300 °C. All imines were electrochemically active and exhibited low energy band gaps below 2 eV (except for one imine with Eg = 2.39 eV) determined on the basis of cyclic voltammetry. Most of the azomethines were emissive in solution and in the solid state. Some of them showed both S1 (first excited state) emission and S2 (second excited state) emission or only fluorescence from higher excited state, which is first time observed for azomethines. The imine with the most promising properties was tested in a light-emitting diode, and its ability for emission of light under external voltage was demonstrated

New thiophene imines acting as hole transporting materials in photovoltaic devices

ASAP Article - Articles ASAP (as soon as publishable) are posted online and available to view immediately after technical editing, formatting for publication, and author proofing.Five new unsymmetric thiophene imines end-capped with an electron-donating amine (−NH2) group were obtained using a simple synthetic route, that is, the melt condensation of 2,5-diamino-thiophene-3,4-dicarboxylic acid diethyl ester with commercially available aldehydes. Their thermal stability and electrochemical and photophysical (absorption (UV−vis) and photoluminescence (PL)) properties were examined and density functional theory calculations were performed. The imines were thermally stable above 200 °C. They underwent reduction and oxidation processes and exhibited an energy band gap electrochemically estimated between 1.81 and 2.44 eV. They absorbed radiation from the UV and visible range to 480 nm and showed weak light emission. These compounds were investigated as hole transporting materials in solar cells with the structure FTO/b-TiO2/m-TiO2/perovskite/imine/Au. The highest photoelectric conversion efficiency was observed for compounds with a morpholine derivative substituent

New acceptor-donor-acceptor systems based on bis-(imino-1,8- naphthalimide)

In this paper, six novel symmetrical bis-(imino-1,8-naphthalimides) differing in core and N-substituent structure were synthesized, and their thermal (TGA, DSC), optical (UV-Vis, PL), electrochemical (DPV, CV) properties were evaluated. The compounds were stable to 280 C and could be transferred into amorphous materials. Electrochemical investigations showed their ability to occur reductions and oxidations processes. They exhibited deep LUMO levels of about -3.22 eV and HOMO levels above -5.80 eV. The optical investigations were carried out in the solutions (polar and non-polar) and in films and blends with PVK:PBD. Bis-(imino-1,8-naphthalimides) absorbed electromagnetic radiation in the range of 243–415 nm and emitted light from blue to yellow. Their capacity for light emission under voltage was preliminarily tested in devices with an active layer consisting of a neat compound and a blend with PVK:PBD. The diodes emitted green or red light

Synthesis and Thermal, Photophysical, Electrochemical Properties of 3,3-di[3-Arylcarbazol-9-ylmethyl]oxetane Derivatives

Novel oxetane-functionalized derivatives were synthesized to find the impact of carbazole substituents, such as 1-naphtyl, 9-ethylcarbazole and 4-(diphenylamino)phenyl, on their thermal, photophysical and electrochemical properties. Additionally, to obtain the optimized ground-state geometry and distribution of the frontier molecular orbital energy levels, density functional theory (DFT) calculations were used. Thermal investigations showed that the obtained compounds are highly thermally stable up to 360 C, as molecular glasses with glass transition temperatures in the range of 142–165 C. UV–Vis and photoluminescence studies were performed in solvents of differing in polarity, in the solid state as a thin film on glass substrate, and in powders, and were supported by DFT calculations. They emitted radiation both in solution and in film with photoluminescence quantum yield from 4% to 87%. Cyclic voltammetry measurements revealed that the materials undergo an oxidation process. Next, the synthesized molecules were tested as hole transporting materials (HTM) in perovskite solar cells with the structure FTO/b-TiO2/m-TiO2/perovskite/HTM/Au, and photovoltaic parameters were compared with the reference device without the oxetane derivatives

Symmetrical and asymmetrical imino-naphthalimides in perovskite solar cells

In perovskite solar cells, series of symmetrical and asymmetrical imino-naphthalimides were tested as hole-transporting materials. The compounds exhibited high thermal stability at the temperature of the beginning of thermal decomposition above 300 °C. Obtained imino-naphthalimides were electrochemically active and their adequate energy levels confirm the application possibility in the perovskite solar cells. Imino-naphthalimides were absorbed with the maximum wavelength in the range from 331 nm to 411 nm and emitted light from the blue spectral region in a chloroform solution. The presented materials were tested in the perovskite solar cells devices with a construction of FTO/b-TiO2/m-TiO2/perovskite/ HTM/Au. For comparison, the reference perovskite cells were also performed (without hole-transporting materials layer). Of all the proposed materials tested as hole-transporting materials, the bis-(imino-naphthalimide) containing in core the triphenylamine structure showed a power conversion efficiency at 1.10% with a short-circuit current at 1.86 mA and an open-circuit voltage at 581 mV

Synthesis and Characterization of New Conjugated Azomethines End-Capped with Amino-thiophene-3,4-dicarboxylic Acid Diethyl Ester

A new series of thiophene-based azomethines differing in the core structure was synthesized. The effect of the central core structure in azomethines on the thermal, optical and electrochemical properties was investigated. The obtained compounds exhibited the ability to form a stable amorphous phase with a high glass transition temperature above 100 °C. They were electrochemically active and undergo oxidation and reduction processes. The highest occupied (HOMO) and the lowest unoccupied molecular (LUMO) orbitals were in the range of −3.86–−3.60 eV and −5.46–−5.17 eV, respectively, resulting in a very low energy band gap below 1.7 eV. Optical investigations were performed in the solvents with various polarity and in the solid state as a thin film deposited on a glass substrate. The synthesized imines absorbed radiation from 350 to 600 nm, depending on its structure and showed weak emission with a photoluminescence quantum yield below 2.5%. The photophysical investigations were supported by theoretical calculations using the density functional theory. The synthesized imines doped with lithium bis-(trifluoromethanesulfonyl)imide were examined as hole transporting materials (HTM) in hybrid inorganic-organic perovskite solar cells. It was found that both a volume of lithium salt and core imine structure significantly impact device performance. The best power conversion efficiency (PCE), being about 35–63% higher compared to other devices, exhibited cells based on the imine containing a core tiphenylamine unit