ADDA and ADADA systems based on triphenylamine as molecular donors for organic photovoltaics

Three molecular donor (D) acceptor (A) systems of structure A–D–A–D–A as well as an A–D–D–A compound have been synthesized by spatial extension of reference D–A system containing a triphenylamine donor block (5). UV–Vis absorption spectroscopy, cyclic voltammetry and theoretical calculations show that the presence of a median acceptor group has limited effect on the internal charge transfer while direct dimerization leads to an increase of the effective conjugation length. A cursory evaluation of the new compounds as donor material in bilayer solar cells using fullerene C60 as the acceptor material shows that the presence of a median acceptor has deleterious effect on conversion efficiency while the simple dimerization of the molecule leads to a substantial improvement of the short-circuit current density and efficiency

Manipulation of the electronic and photovoltaic properties of materials based on small push-pull molecules by substitution of the arylamine donor block by aliphatic groups

Push-pull molecules with an arylamine donor block connected to a dicyanovinyl acceptor via a thienyl π-conjugating spacer have been synthesized in order to analyze the effects of replacing an outer phenyl ring of the triphenylamine (TPA) block of a reference compound by methyl, hexyl, heptafluoropentyl and dioxaoctyl groups. Optical, electrochemical and X-ray diffraction data show that these substitutions have minor influence on the energy levels of the molecule but exert a considerable effect on the structure, optical, electrical and photovoltaic properties of the resulting materials

Linearly π-conjugated oligothiophenes as simple metal-free sensitizers for dye-sensitized solar cells

Four linear oligothiophenes containing 4, 5 and 7 thiophene rings substituted by a variable number of octyl chains attached at the beta-position of some of the thiophene rings and possessing a terminal cyanoacrylic acid anchoring group have been synthesized. Results of UV-Vis absorption spectroscopy and cyclic voltammetry show that as expected the extension of the π-conjugated system leads to a decrease of the optical gap with an increase of the HOMO level. The four compounds have been evaluated as sensitizers in dye-sensitized solar cells (DSSCs) using a iodide/triiodide liquid electrolyte and the results are discussed in terms of the structure–property relationship with regard to the extension of the conjugated system and the number and position of the octyl side chains using N719 as the reference system. A power conversion efficiency of ~7.30% corresponding to 90% of the value given by N719 under identical conditions has been obtained with one of the heptamers

Effects of Anthryl Groups on the Charge Transport and Photovoltaic Properties of Small Triarylamine-Based Donor-Acceptor Molecules: A Joint Experimental and Theoretical Study

The effects of replacing one of the outer phenyl rings of triphenylamine by 2-anthryl and 9-anthryl groups of triphenylamine (TPA) have been investigated on two small push-pull molecules consisting of a triarylamine donor block connected to a dicyanovinyl acceptor via a thienyl spacer. UV-Vis absorption, cyclic voltammetry and theoretical calculations show that the mode of linkage of the anthryl group has a limited influence on the electronic properties of the molecule compared to reference compound based on TPA. However experimental and theoretical results show that this simple structural modification exerts a major impact on the hole-mobility of the resulting materials and thus on their efficiency as donor in planar heterojunction solar cells

Enhanced hydrogen evolution reaction performance of anatase–rutile TiO2 heterojunction via charge transfer from rutile to anatase

This is the final version. Available on open access from the Royal Society of Chemistry via the DOI in this recordIn light of recent doubts surrounding the industrial viability of photo(electro)catalysis technology for sustainable hydrogen production, it becomes imperative to align materials development with rationalized synthesis protocols. In this study, we present an innovative technique utilizing atmospheric-pressure chemical vapor deposition (APCVD) to rapidly produce TiO2 in just 5 minutes using pure TiCl4 as the sole reagent. The resulting photoanode exhibits exceptional photoelectrochemical (PEC) water-splitting performance, achieving a photocurrent density of 2.06 mA cm−2 at 1.23 V RHE. Moreover, the photoanode demonstrates sustained operation for 16 hours, leading to the successful collection of 138 μmol of H2 and 62 μmol of O2. These remarkable results are attributed to the controlled formation of an anatase–rutile phase-junction, the presence of well-balanced oxygen vacancies, and the bifrustum nanoparticle–nanoflake structure with a unique light trapping effect and large surface area. Density functional theory calculations confirm that the water-splitting reaction primarily occurs at undercoordinated Ti and O atoms in both anatase and rutile TiO2. Notably, the calculated Gibbs free energy values for the hydrogen evolution reaction (HER) differ significantly between rutile (−0.86 eV) and anatase TiO2 (0.22 eV). In the heterojunction, charge transfer enhances the HER performance through shared electronic density, resulting in a synergistic effect that surpasses the capabilities of individual surfaces and underscores the importance of electronic interactions within the junction.Universiti Kebangsaan MalaysiaCenter of Excellence for Innovation in ChemistryProgram Management Unit for Human Resources & Institutional Development, Research and InnovationHuman Resource Development in Science Project Science Achievement Scholarship of Thailand (SAST