Electrical and optical properties of reduced graphene oxide thin film deposited onto polyethylene terephthalate by spin coating technique.

We present the reduction of solution processed graphene oxide films by hydrogen iodide vapor. The films were studied by Raman spectroscopy and Fourier-transform infrared spectroscopy and its optoelectronic properties characterized. We obtained reduced graphene oxide films on polyethylene terephthalate flexible substrates with good electrical properties, 3.74×10-6 Ω·m, and high optical transmittance of 70% in the visible range. The fabricated layers contain graphene sheets with sizes up to ∼10 µm long and ∼6 µm wide. The presented solution, with highly concentrated processed graphene oxide, could be used as printing ink for manufacturing transparent and conductive electrodes on plastic substrates without the requirement of elevated temperatures.

Influence of the solvent on the sensitization of nanostructured electrodes of TiO2 for solar cells sensitized with a natural dye extracted from purple corn: Molecular dynamic simulation and experimental validation.

This study uses molecular dynamics (MD) simulations and experiments to explore the interaction between titanium dioxide (TiO2) and cyanidin-3-glucoside (C3G), the main compound in purple corn, in the context of sensitized solar cells. dyes (DSSCs). Different proportions of water and ethanol in the solvent were applied. MD revealed the effective chemisorption of C3G and significant variations in the equilibrium enthalpy, indicating the influence of the solvent composition on the stability of the TiO2/C3G system. The negative adsorption energies (EAds) reveal favourable adsorption processes. A possible formation of solvation shells was observed near the TiO2 nanoparticle. The experimental results supported the simulation predictions, highlighting the system with 25 % water and 75 % ethanol (W1E3) as the most efficient. The formation of solvation shells facilitates C3G adsorption, improving anchoring and reducing unwanted electron recombinations. The results provide essential information for the selection of optimal solvents in future photovoltaic applications, contributing to the improvement of the performance of these solar cells.

Betanin dye extracted from ayrampo (Opuntia soehrensii) seeds to develop dye-sensitized solar cells.

Pigments extracted from ayrampo seeds of the Peruvian-native prickly pear (Opuntia soehrensii) were used in dye-sensitized solar cells with promising efficiencies. The performance of the solar cells was then improved via the addition of citric acid to stabilise the photosensitive dye, and an efficiency of 1.41% was achieved with current output remaining stable after 7 days. Upon testing in low-light conditions, the solar conversion efficiency of devices increased to 4%. This paper not only highlights the potential of natural sensitizers in DSSCs but also shows that simple extraction and gentle handling methods can contribute to the device performance.

Extraction of 2'-O-apiosyl-6'-O-crotonic acid-betanin from the ayrampo seed (Opuntia soehrensii) cuticle and its use as an emitting layer in an organic light-emitting diode.

The molecule 2'-O-apiosyl-6'-O-crotonic acid-betanin (called Achkiy) was obtained after an ecofriendly and low-cost purification process of the extract from the ayrampo seed cuticle. Results from EDS give us an idea of the organic elements present in the ayrampo cuticle layer composed of carbon, oxygen and nitrogen. Further characterization analysis of ayrampo extract by Fourier Transform Infrared Spectrophotometry (FTIR) corroborated the presence of characteristic functional groups corresponding to carboxyl, carbonyls, hydroxyls and secondary amines. On the other hand, we have confirmed by absortion peak the glucose, apiosyl, crotonic acid and betanin at 227 nm, 276 nm, 291 nm and 534 nm bands respectively. Mass Spectrometry (MS) characterization was used finally to identify the electroactive Achkiy molecule. This molecule was tested in an Organic Light Emitting Diode (OLED) achieving a luminance of 4.8 Cd m-2 when bias voltage of 16.5 V and a current of 34.1 mA was applied. In addition, the irradiance generated by the Achkiy layer reaches a value of ≈ 113.3 µW m-2 emitting light with a λ ≈ 390.10 nm. These preliminary results report an interesting molecule extracted from a natural pigment wich emits light in the blue region.