This paper presents results of a study that allowed identifying states of traps in thin films of hybrid organic-inorganic perovskite compounds based on methylammonium lead halide with different compositions CH3NH3PbX3 (X is Cl, Br or I) prepared by spin-coating, through Thermally Stimulated Current (TSC) measurements. Special emphasis was done in studying the influence of the composition and adsorption of oxygen on the depth of traps and on the density of states associated with trapping centers. Deconvolution of the TSC curves obtained from measurements made inside a vacuum chamber under different oxygen partial pressures, revealed the presence of traps centers whose activation energies are affected by the oxygen concentration. It was also found that TSC peaks do not appear in TSC measurements carried out at pressures less than 0.1 mbar, indicating that the possible nature of the identified traps centers is related to oxygen adsorbed superficially and/or located into the grain boundaries.

Bananas are one of the most important crops worldwide. However, a large amount of residual lignocellulosic biomass is generated during its production and is currently undervalued. These residues have the potential to be used as feedstock in bio-based processes with a biorefinery approach. This work is based on the valorization of banana leaf and has the following objectives (i) to determine the effect of certain physical and environmental factors on the concentration of glucose present in banana leaf extract (BLE), using a statistical regression model; (ii) to obtain Bacterial Nanocellulose (BNC), using BLE (70% v/v) and kombucha tea as fermentation medium. In addition, the physicochemical properties of BNC were evaluated by X-ray diffraction (XRD), Fourier transform infrared (FTIR), and thermogravimetric analysis (TGA). The results indicate that storage time, location, leaf color, and petiole type are factors related to BLE concentration, which is reduced by approximately 28.82% and 64.32% during storage times of five days. Regarding BNC biosynthesis, the results indicate that the highest yield, 0.031 g/g, was obtained at 21 days. Furthermore, it was determined that the highest production rate was 0.11 gL−1h−1 at 11 days of fermentation. By FTIR, it was determined that the purification step with NaOH (3M) should be carried out for approximately two hours. This research supports the development of a circular bioeconomy around the banana value chain, as it presents a way of bioprocessing residual biomass that can be used to produce bioproducts.

Thin films of CH3NH3PbI3 and (NH2)2CHPbI3 (from now on abbreviated as MAPI and FAPI respectively), with perovskite structure were prepared by sequential evaporation of lead iodide (PbI2) and methylammonium iodide (MAI) or formamidinium iodide (FAI), with special emphasis on the optimization of its optical, morphologic, and structural properties. For this, the evaporation process was automatically controlled with a system developed using virtual instrumentation (VI) that allows electronic control of both evaporation sources temperature and precursors deposition rates, using proportional integral derivative (PID) and pulse width modulation (PWM) control algorithms developed with the LabView software. Using X-ray diffraction (XRD), information was obtained regarding the phase and crystalline structure of the studied samples as well as the effect of the main deposition parameters on crystallite size and microstrain. We also studied the influence of the main deposition parameters on the optical and morphological properties through measurements of spectral transmittance and scanning electron microscopy (SEM) respectively. It was found that the implemented method of sequential evaporation allows preparing, with a high degree of reproducibility, single phase MAPI and FAPI thin films with appropriate properties to be used as active layer in hybrid solar cells. The applicability of MAPI and FAPI thin films as active layer in photovoltaic devices has been demonstrated by using them in solar cells with structure: FTO/ZnO/MAPI(or FAPI)/P3HT/Au.

The hybrid halide perovskite methyl ammonium lead iodide thiocyanate – (CH3NH3)Pb(SCN)2I2 – is synthesized both as a powder and as a thin film. The crystal structure and key optical properties (band gap) are determined by diffuse reflectance spectra and X‐ray diffraction (Rietveld refinement) measurements and compared to density functional theory (DFT) state‐of‐the‐art calculations. It is found that the refined orthorhombic crystal structure presents 2D‐layer confinement, and that the optical band gap presented in this work does confirm some previous reports and rebuts other results, too.