New insights into the structure of glycols and derivatives: a comparative X-ray diffraction, Raman and molecular dynamics study of ethane-1,2-diol, 2-methoxyethan-1-ol and 1,2-dimethoxy ethane

In this study, we report a detailed experimental and theoretical investigation of three glycol derivatives, namely ethane-1,2-diol, 2-methoxyethan-1-ol and 1,2-dimethoxy ethane. For the first time, the X-ray spectra of the latter two liquids was measured at room temperature, and they were compared with the newly measured spectrum of ethane-1,2-diol. The experimental diffraction patterns were interpreted very satisfactorily with molecular dynamics calculations, and suggest that in liquid ethane-1,2-diol most molecules are found in gauche conformation, with intramolecular hydrogen bonds between the two hydroxyl groups. Intramolecular H-bonds are established in the mono-alkylated diol, but the interaction is weaker. The EDXD study also evidences strong intermolecular hydrogen-bond interactions, with short O···O correlations in both systems, while longer methyl-methyl interactions are found in 1,2-dimethoxy ethane. X-ray studies are complemented by micro Raman investigations at room temperature and at 80 °C, that confirm the conformational analysis predicted by X-ray experiments and simulations

Stability of dye-sensitized solar cells under extended thermal stress

In the last few decades, dye-sensitized solar cell (DSC) technology has been demonstrated to be a promising candidate for low cost energy production due to cost-effective materials and fabrication processes. Arguably, DSC stability is the biggest challenge for making this technology appealing for industrial exploitation. This work provides further insight into the stability of DSCs by considering specific dye–electrolyte systems characterized by Raman and impedance spectroscopy analysis. In particular, two rutheniumbased dyes, Z907 and Ru505, and two commercially available electrolytes, namely, the high stability electrolyte (HSE) and solvent-free Livion 12 (L-12), were tested. After 4700 h of thermal stress at 85 1C, the least stable device composed of Z907/HSE showed an efficiency degradation rate of B14%/1000 h, while the Ru505/L-12 system retained 96% of its initial efficiency by losing B1% each 1000 h. The present results show a viable route to stabilize the DSC technology under prolonged annealing conditions complying with the IEC standard requirements

Spin coating immobilisation of C-N-TiO2 Co-Doped nano catalyst on glass and application for photocatalysis or as electron transporting layer for perovskite solar cells

Producingactivethinfilmscoatedonsupportsresolvesmanyissuesofpowder-basedphoto catalysis and energy harvesting. In this study, thin films of C-N-TiO2 were prepared by dynamic spin coating of C-N-TiO2 sol-gel on glass support. The effect of spin speed and sol gel precursor to solvent volume ratio on the film thickness was investigated. The C-N-TiO2-coated glass was annealed at 350◦C at a ramping rate of 10◦C/min with a holding time of 2 hours under a continuous flow of dry N2. The C-N-TiO2 films were characterised by profilometry analysis, light microscopy (LM), and scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS). The outcomes of this study proved that a spin coating technique followed by an annealing process to stabilise the layer could be used for immobilisation of the photo catalyst on glass. The exposure of C-N-TiO2 films to UV radiation induced photocatalytic decolouration of orange II (O.II) dye. The prepared C-N-TiO2 films showed a reasonable power conversion efficiency average (PCE of 9%) with respect to the reference device (15%). The study offers a feasible route for the engineering of C-N-TiO2 films applicable to wastewater remediation processes and energy harvesting in solar cell technologies

Mixed Cation Halide Perovskite under Environmental and Physical Stress

Despite the ideal performance demonstrated by mixed perovskite materials when used as active layers in photovoltaic devices, the factor which still hampers their use in real life remains the poor stability of their physico-chemical and functional properties when submitted to prolonged permanence in atmosphere, exposure to light and/or to moderately high temperature. We used high resolution photoelectron spectroscopy to compare the chemical state of triple cation, double halide Cs [Formula: see text] (FA [Formula: see text] MA [Formula: see text]) [Formula: see text] Pb(I [Formula: see text] Br [Formula: see text]) [Formula: see text] perovskite thin films being freshly deposited or kept for one month in the dark or in the light in environmental conditions. Important deviations from the nominal composition were found in the samples aged in the dark, which, however, did not show evident signs of oxidation and basically preserved their own electronic structures. Ageing in the light determined a dramatic material deterioration with heavily perturbed chemical composition also due to reactions of the perovskite components with surface contaminants, promoted by the exposure to visible radiation. We also investigated the implications that 2D MXene flakes, recently identified as effective perovskite additive to improve solar cell efficiency, might have on the labile resilience of the material to external agents. Our results exclude any deleterious MXene influence on the perovskite stability and, actually, might evidence a mild stabilizing effect for the fresh samples, which, if doped, exhibited a lower deviation from the expected stoichiometry with respect to the undoped sample. The evolution of the undoped perovskites under thermal stress was studied by heating the samples in UHV while monitoring in real time, simultaneously, the behaviour of four representative material elements. Moreover, we could reveal the occurrence of fast changes induced in the fresh material by the photon beam as well as the enhanced decomposition triggered by the concurrent X-ray irradiation and thermal heating

Effects of crystal morphology on the hot-carrier dynamics in mixed-cation hybrid lead halide perovskites

Ultrafast pump-probe spectroscopies have proved to be an important tool for the investigation of charge carriers dynamics in perovskite materials providing crucial information on the dynamics of the excited carriers, and fundamental in the development of new devices with tailored photovoltaic properties. Fast transient absorbance spectroscopy on mixed-cation hybrid lead halide perovskite samples was used to investigate how the dimensions and the morphology of the per-ovskite crystals embedded in the capping (large crystals) and mesoporous (small crystals) layers affect the hot-carrier dynamics in the first hundreds of femtoseconds as a function of the excitation energy. The comparative study between samples with perovskite deposited on substrates with and without the mesoporous layer has shown how the small crystals preserve the temperature of the carriers for a longer period after the excitation than the large crystals. This study showed how the high sensitivity of the time-resolved spectroscopies in discriminating the transient response due to the different morphology of the crystals embedded in the layers of the same sample can be applied in the general characterization of materials to be used in solar cell devices and large area modules, providing further and valuable information for the optimization and enhancement of stability and efficiency in the power conversion of new perovskite-based devices

Graphene-Based Interconnects for Stable Dye-Sensitized Solar Modules

We present Z-Type Dye Sensitized Solar Modules (DSSMs) with screen printed graphene-based vertical interconnects. This prevents corrosion of interconnects in contact with electrolytic species, unlike conventional Ag interconnects. By enlarging the width of single cells, or by increasing the number of cells, we get an enhancement of the aperture power conversion efficiency ∼+12% with respect to Ag-based modules, with 1000 h stability under 85 °C stress test. This paves the way to original design layouts with decreased dead area and increased generated power per aperture area

Effect of calcination time on the physicochemical properties and photocatalytic performance of carbon and nitrogen co-doped TiO2 nanoparticles

The application of highly active nano catalysts in advanced oxidation processes (AOPs) improves the production of non-selective hydroxyl radicals and co-oxidants for complete remediation of polluted water. This study focused on the synthesis and characterisation of a highly active visible light C–N-co-doped TiO2 nano catalyst that we prepared via the sol-gel method and pyrolysed at 350 ◦C for 105 min in an inert atmosphere to prevent combustion of carbon moietie

Laser Processing Optimization for Large-Area Perovskite Solar Modules

The industrial exploitation of perovskite solar cell technology is still hampered by the lack of repeatable and high-throughput fabrication processes for large-area modules. The joint efforts of the scientific community allowed to demonstrate high-performing small area solar cells; however, retaining such results over large area modules is not trivial. Indeed, the development of deposition methods over large substrates is required together with additional laser processes for the realization of the monolithically integrated cells and their interconnections. In this work, we develop an efficient perovskite solar module based on 2D material engineered structure by optimizing the laser ablation steps (namely P1, P2, P3) required for shaping the module layout in series connected sub-cells. We investigate the impact of the P2 and P3 laser processes, carried out by employing a UV pulsed laser (pulse width = 10 ns; λ = 355 nm), over the final module performance. In particular, a P2 process for removing 2D material-based cell stack from interconnection area among adjacent cells is optimized. Moreover, the impact of the P3 process used to isolate adjacent sub-cells after gold realization over the module performance once laminated in panel configuration is elucidated. The developed fabrication process ensures high-performance repeatability over a large module number by demonstrating the use of laser processing in industrial production