Investigations of new phenothiazine-based compounds for dye-sensitized solar cells with theoretical insight

New D- -D- -A low-molecular-weight compounds, based on a phenothiazine sca old linked via an acetylene unit with various donor moiety and cyanoacrylic acid anchoring groups, respectively, were successfully synthesized. The prepared phenothiazine dyes were entirely characterized using nuclear magnetic resonance (NMR) spectroscopy and elemental analysis. The compounds were designed to study the relationship between end-capping donor groups’ structure on their optoelectronic and thermal properties as well as the dye-sensitized solar cells’ performance. The e ect of -conjugation enlargement by incorporation of di erent heterocyclic substituents possessing various electron–donor a nities was systematically experimentally and theoretically examined. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations were implemented to determine the electronic properties of the novel molecules

Examination of the effect of selected factors on the photovoltaic response of dye-sensitized solar cells

The impact of photoanode preparation on the photovoltaic performance of dye-sensitized solar cells was investigated. The effects of titanium dioxide layer thickness, type of solvent and immersion time used for photoanode fabrication, and addition of coadsorbents and a cosensitizer on photon-to-current conversion efficiency and photovoltaic parameters were studied. Commercially available N719 and dyes prepared in our research group, 5,5′-bis(2-cyano-1-acrylic acid)-2,2′-bithiophene and 2-cyano-3-(2,2′:5′,2″-terthiophen-5-yl)acrylic acid, were applied as sensitizers. The effect of studied factors on UV–vis properties and morphology, that is, the root-mean-square roughness of the photoanode, was examined and correlated with the photovoltaic response of the constructed devices. Additionally, the amount of dye molecules adsorbed to the TiO2 was investigated. It was found that all considered factors significantly impacted photovoltaic parameters. Also, the photoanode stability was tested by measuring photovoltaic parameters after 14 months

Impact of TiO2 nanostructures on dye-sensitized solar cells performance

The effect of TiO2 nanostructures such as nanoparticles, nanowires, nanotubes on photoanode properties, and dye-sensitized solar cells photovoltaic parameters were studied. The series of dye-sensitized solar cells based on two dyes, that is, commercially N719 and synthesized 3,70- bis(2-cyano-1-acrylic acid)-10-ethyl-phenothiazine were tested. Additionally, the devices containing a mixture of this sensitizer and chenodeoxycholic acid as co-adsorbent were fabricated. The amount of adsorbed dye molecules to TiO2 was evaluated. The prepared photoanodes with different TiO2 nanostructures were investigated using UV-Vis spectroscopy, optical, atomic force, and scanning electron microscopes. Photovoltaic response of constructed devices was examined based on currentvoltage characteristics and electrochemical impedance spectroscopy measurements. It was found that the highest UV-Vis absorption exhibited the photoanode with nanotubes addition. This indicates the highest number of sensitizer molecules anchored to the titanium dioxide photoanode, which was subsequently confirmed by dye-loading tests. The highest power conversion efficiency was (6.97%) for solar cell containing nanotubes and a mixture of the dyes with a co-adsorbent

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

Photoelectrochemical and thermal characterization of aromatic hydrocarbons substituted with a dicyanovinyl unit

Seven aromatic hydrocarbons bearing a dicyanovinyl unit were prepared to determine the relationship between both the number of aromatic rings and location of acceptor substituent on their thermal and optoelectronic properties. Additionally, the density functional theory calculations were performed. The obtained compounds showed temperatures of the beginning of thermal decomposition in the range of 137 – 289 °C, being above their respective melting points found between 88 and 248 °C. They were electrochemically active and showed quasi-reversible reduction process (except for 2-(phen-1- yl)methylene)malononitrile). Electrochemically estimated energy band gaps were below 3.0 eV, in the range of 2.10 – 2.50 eV. The absorption and emission spectra were recorded in CHCl3 and NMP and in solid state. All compounds strongly absorbed radiation with absorption maximum ranging from 307 to 454 nm ascribed to the intramolecular charge transfer between the donor and acceptor units. The aromatic hydrocarbons were luminescent in all investigated media and exhibited higher photoluminescence quantum yields in the solid state due to the aggregation induced emission phenomena. Electroluminescence ability of selected compounds was tested in a diode with guest-host configuration. Additionally, the selected compound together with a commercial N719 was applied in the dye-sensitized solar cell

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 benzo[h]quinolin-10-ol derivatives as co-sensitizers for DSSCs

New benzo[h]quinolin-10-ol derivatives with one or two 2-cyanoacrylic acid units were synthesized with a good yield in a one-step condensation reaction. Chemical structure and purity were confirmed using NMR spectroscopy and elemental analysis, respectively. The investigation of their thermal, electrochemical and optical properties was carried out based on differential scanning calorimetry, cyclic voltammetry, electronic absorption and photoluminescence measurements. The analysis of the optical, electrochemical and properties was supported by density functional theory studies. The synthesized molecules were applied in dye-sensitized solar cells as sensitizers and cosensitizers with commercial N719. The thickness and surface morphology of prepared photoanodes was studied using optical, scanning electron and atomic force microscopes. Due to the utilization of benzo[h]quinolin-10-ol derivatives as co-sensitizers, the better photovoltaic performance of fabricated devices compared to a reference cell based on a neat N719 was demonstrated. Additionally, the effect of co-adsorbent chemical structure (cholic acid, deoxycholic acid and chenodeoxycholic acid) on DSSC efficiency was explained based on the density functional theory

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

Effect of photoanode structure and sensitization conditions on the photovoltaic response of dye-sensitized solar cells

This work summarises investigations focused on the photoanode impact on the photovoltaic response of dye-sensitized solar cells. This is a comparison of the results obtained by the authors’ research team with literature data. The studies concern the effect of the chemical structure of the applied dye, TiO₂ nanostructure, co-adsorbents addition, and experimental conditions of the anode preparation. The oxide substrates were examined using a scanning electron microscope to determine the thickness and structure of the material. The TiO₂ substrates with anchored dye molecules were also tested for absorption properties in the UV-Vis light range, largely translating into current density values. Photovoltaic parameters of the fabricated devices with sandwich structure were obtained from current-voltage measurements. During tests conducted with the N719 dye, it was found that devices containing an 8.4 μm thick oxide semiconductor layer had the highest efficiency (5.99%). At the same time, studies were carried out to determine the effect of the solvent and it was found that the best results were obtained using an ACN : tert-butanol mixture (5.46%). Next, phenothiazine derivatives (PTZ-1–PTZ-6) were used to prepare the devices; among the prepared solar cells, the devices containing PTZ-2 and PTZ-3 had the highest performance (6.21 and 6.22%, respectively). Two compounds designated as Th-1 and M-1 were used to prepare devices containing a dye mixture with N719

An Investigation of the Thermal Transitions and Physical Properties of Semiconducting PDPP4T:PDBPyBT Blend Films

This work focuses on the study of thermal and physical properties of thin polymer films based on mixtures of semiconductor polymers. The materials selected for research were poly [2,5-bis(2-octyldodecyl)-pyrrolo [3,4-c]pyrrole-1,4(2H,5H)-dione-3,6-diyl)-alt-(2,2′;5′,2″;5″,2′′′-quater-thiophen-5,5′′′-diyl)]—PDPP4T, a p-type semiconducting polymer, and poly(2,5-bis(2-octyldodecyl)-3,6-di(pyridin-2-yl)-pyrrolo [3,4-c]pyrrole-1,4(2H,5H)-dione-alt-2,2′-bithiophene)—PDBPyBT, a high-mobility n-type polymer. The article describes the influence of the mutual participation of materials on the structure, physical properties and thermal transitions of PDPP4T:PDBPyBT blends. Here, for the first time, we demonstrate the phase diagram for PDPP4T:PDBPyBT blend films, constructed on the basis of variable-temperature spectroscopic ellipsometry and differential scanning calorimetry. Both techniques are complementary to each other, and the obtained results overlap to a large extent. Our research shows that these polymers can be mixed in various proportions to form single-phase mixtures with several thermal transitions, three of which with the lowest characteristic temperatures can be identified as glass transitions. In addition, the RMS roughness value of the PDPP4T:PDBPyBT blended films was lower than that of the pure materials