Sergey A. Kozyukhin

Three novel D–π–A dyes (PtD 1–3) based on a [1,2,4]triazolo[1,5-a]pteridine (TPt) acceptor–anchoring unit and a thiophene π-bridge were synthesized through a modular approach involving nucleophilic aromatic substitution of hydrogen and Suzuki–Miyaura cross-coupling. The electron-donating fragments were varied to investigate their influence on the electronic structure and photophysical properties of the resulting compounds. Their optical and electrochemical properties were examined using experimental and computational methods, including DFT, TD-DFT, and quantitative hole–electron analysis. All three dyes exhibited absorption bands with intramolecular charge-transfer character and energy-level alignment compatible with electron injection into TiO2, consistent with the estimated electron injection efficiencies of 77.7–91.5%. The synthesized dyes were further subjected to a preliminary evaluation as sensitizers in dye-sensitized solar cells (DSSCs). Among the investigated compounds, PtD 1 showed the highest power conversion efficiency of 1.28%. Differences in photovoltaic performance were associated with variations in light harvesting, dye regeneration, and other device-relevant parameters rather than dye loading alone. These findings demonstrate the feasibility of using the TPt framework as an acceptor–anchoring platform and provide a basis for further development of organic dyes for DSSC applications.

The possibility of forming periodic surface structures in amorphous GeTe and Sb ₂ Te ₃ thin films irradiated by 1030-nm femtosecond laser pulses has been studied. The inclusion of nonlinear absorption and photoinduced electron generation within the framework of the surface electromagnetic wave excitation theory allows the prediction of the formation or absence of surface gratings in these materials induced by ultrashort laser pulses. The simulation results are consistent with experimental data.

Laser-induced periodic surface structures (LIPSS) on chalcogenide glassy semiconductors are of great interest in relation with creating polarization-sensitive optical elements. This study investigates the formation of LIPSS on the surface of As ₅₀ Se ₅₀ amorphous film, fabricated by thermal vacuum deposition, under femtosecond laser irradiation in the wavelength range from 400 to 800 nm. The periods of various LIPSS types depend linearly on the laser wavelength. The measured birefringence of so-called low spatial frequency LIPSS, formed by different irradiation wavelengths, are in the 10–85 nm range. The maximum birefringence of 85 nm was obtained for structures irradiated at a 480 nm wavelength. A significant decrease in birefringence was observed at a wavelength of 800 nm, which may be due to the formation of a less pronounced and more disordered surface relief caused by less effective absorption of modifying laser radiation with photon energy lower than optical band gap of As ₅₀ Se ₅₀ . Decreased optical absorption observed in As ₅₀ Se ₅₀ films with LIPSS is caused by increased light scattering on the surface relief.

Heterostructures based on ZnO nanorods and CsPbBr3 nanocrystals were investigated for their potential as semiconductor SERS substrates. We found that ZnO morphology governs the efficiency of interfacial energy transfer, leading to enhanced photoluminescence under 390 nm excitation and a noticeable reduction of the bandgap in the composites. Raman analysis revealed a pronounced intensity enhancement and the emergence of low-frequency CsPbBr3 modes isolated via Gaussian deconvolution, which confirms the SERS-like behavior of the hybrid structures. Our results highlight the strong prospects of ZnO/CsPbBr3 heterostructures for sensing and optoelectronic applications. Гетероструктуры на основе наностержней ZnO и наночастиц CsPbBr3 были ис­следованы с целью оценки их потенциала в качестве полупроводниковых SERS-субстратов. Было выявлено, что морфология ZnO определяет эффективность межфазного переноса энергии, уве­личивая фотолюминесценцию при длине возбуждения 390 нм и вызывая снижение ширины за­прещенной зоны в композитах. Анализ спектров комбинационного рассеяния выявил значитель­ное усиление интенсивности и появление низкочастотных мод CsPbBr3, выделенных с помощью гауссовой деконволюции, что подтверждает SERS-подобное поведение гибридных структур. Полученные результаты демонстрируют перспективность ZnO/CsPbBr3-гетероструктур для сен­сорики и оптоэлектронных приложений.

Multifunctional compounds with properties that may be triggered by different external stimuli are highly desirable yet challenging in their design and synthesis. Herein, we report a cyclometalated iridium(III) complex based on bulky 1,2-diphenylphenanthroimidazole (C^N) that can easily change its molecular geometry from trigonal-bipyramidal to octahedral or from a monomeric to dimeric state in response to external stimuli (temperature and solvent variations). The extensive characterization including variable-temperature ¹H NMR, single-crystal and powder X-ray diffraction corroborated by density functional theory calculations strongly indicates that the thermochromic behavior of the complex is attributed to the dimer-monomer transformations both in solution and in the solid state. The five-coordinated monomer instantaneously reacts with coordinating solvents (L = CH₃CN, CH₃OH, pyridine) affording octahedral complexes [Ir(C^N)₂(L)Cl]. Binding constants for the formation of the complexes with acetonitrile and methanol were estimated by UV-vis titration. Enabled by the ability to switch between the alternative structural states depending on the medium, the monomer exhibits an unprecedented combination of properties, including a reversible vapochromic behavior and switchable catalytic activity. As illustrative examples, transfer hydrogenation and photoinduced reductive debromination were successfully performed by using the monomer as a catalyst.

Binary chalcogenides have found a wide range of applications due to the possibility of fast and reversible phase transitions, tunable band gap, and high charge carrier mobility. This paper presents the results of thermal and laser crystallization of InSe thin films deposited by vacuum thermal evaporation of synthesized material and covered with a protective SiO2 layer. The amorphous state of as-deposited InSe thin films was confirmed by Raman spectroscopy. Thermal and laser crystallization processes were studied using electrical resistivity measurements and optical microscopy respectively. The temperature and laser power ranges required for the crystallization of the InSe thin film were determined. The Raman spectroscopy showed that the degree of crystallinity of modified regions of InSe thin films can be tuned by varying the power of laser irradiation. Бинарные халькогенидные соединения нашли широкий спектр применения благодаря возможности быстрого и обратимого фазового перехода, перестраиваемой ширины запрещенной зоны, высокой подвижности носителей заряда. Рассматриваются результаты термической и лазерной кристаллизации тонких пленок InSe, сформированных методом вакуумно-термического испарения синтезированного материала и покрытых защитным слоем SiO2. Аморфное состояние тонких пленок InSe было подтверждено спектроскопией комбинационного рассеяния света. Процессы термической и лазерной кристаллизации были изучены путем измерения электрического сопротивления и с применением оптической микроскопии соответственно. Были получены диапазоны температур и мощностей лазерного воздействия, необходимые для кристаллизации тонкой пленки InSe. Результаты спектроскопии комбинационного рассеяния показали, что степень кристалличности тонких пленок InSe можно подстраивать, варьируя мощность лазерного излучения.

Owing to transparency in the near and middle infrared ranges, nanostructures based on arsenic sulfide (As₂S₃) are of interest for designing integrated optics elements. We investigated laser-induced structural and photoluminescence (PL) changes in thermally evaporated and spin-coated vitreous As₂S₃ films. Pulsed (λ = 515 nm, τ = 300 fs) and continuous (λ = 532 nm) laser irradiation was used as a method allowing structural modification without changing the chemical composition of As₂S₃ films. The results of our study reveal laser-induced formation of sulfur S₈ rings and polymer sulfur chains in the spin-coated films, while the local chemical composition of thermally evaporated films does not change. Laser-induced increase in the PL intensity in the range of 1.6–2.0 eV is observed, which is associated with the creation of defect states near the Urbach edge. Laser irradiation presumably increases the amount of homopolar bonds acting as radiative carrier recombination defects, while paramagnetic defects in a form of S dangling bonds do not contribute to PL.

High‐order harmonic generation (HHG) in solids opens new frontiers in ultrafast spectroscopy of carrier and field dynamics in condensed matter, picometer resolution structural lattice characterization and designing compact platforms for attosecond pulse sources. Nanoscale structuring of solid surfaces provides a powerful tool for controlling the spatial characteristics and efficiency of the harmonic emission. Here we study HHG in a prototypical phase‐change material Ge ₂ Sb ₂ Te ₅ (GST). In this material the crystal phase can be reversibly changed between a crystalline and amorphous phase by light or electric current mediated methods. We show that optical phase‐switching is fully reversible and allows for dynamic control of harmonic emission. This introduces GST as new addition to materials that enable flexible metasurfaces and photonic structures that can be integrated in devices and allow for ultrafast optical control.

Solar energy (SE) research is relevant today, especially as far as dye-sensitized solar cells (DSSC) are concerned, which are third-generation devices. The prospect of their future development lies in the creation of architectural and interior-integrated panels, flexible and portable devices for SE conversion. Examining the properties of their components and their mutual impact is crucial for improving the efficiency of DSSC and moving away from the standard cell design. In this work, we investigated dielectric properties of photoanodes (PhA) for DSSC. The influence of a dye on dielectric properties of PhA is shown. By measuring dielectric properties in the samples, we obtained dielectric permittivity and dielectric loss tangent that ranged from –50 to 150 °C and from 10-1 to 106 Hz. Our results make a significant contribution towards a better understanding of the influence that the dye has on dielectric properties of PhA and can serve to develop new efficient composite materials for new-generation photoelectronic devices. Исследования солнечной энергии актуальны особенно в области изучения и создания сенсибилизированных красителей солнечных элементов (СКСЭ), относящихся к третьему поколению фотовольтаических преобразователей солнечного света. Перспективным направлением является создание архитектурных и интерьерно-интегрированных панелей, гибких и портативных устройств. Изучение свойств функциональных материалов, входящих в структуру СКСЭ, и их влияния друг на друга имеет решающее значение для повышения эффективности, снижения себестоимости производства СКСЭ. В работе исследованы диэлектрические свойства фотоанодов (ФА) для СКСЭ, в частности, диэлектрическая проницаемость и тангенс диэлектрических потерь в диапазоне от –50 до 150 °C и от 10–1–106 Гц, что позволило оценить вклад красителя в диэлектрические свойства диоксида титана. Полученные результаты позволяют понять влияние красителя на механизм проводимости носителей заряда в диоксиде титана и могут быть использованы при разработке материалов для СКСЭ.