Gerardo Larramona

8.6% Efficient CZTSSe Solar Cells Sprayed from Water-Ethanol CZTS Colloidal Solutions.

Copper zinc tin sulfide-selenide, Cu2ZnSn(S1-xSex)4 (CZTSSe), thin film photovoltaic devices were fabricated using a fast and environmentally friendly preparation method, consisting of the following steps: An instantaneous synthesis of a Cu-Zn-Sn-S (no Se) colloid, a nonpyrolytic spray of a dispersion of this colloid in a water-ethanol mixture, and a sequential annealing first in a N2 atmosphere and second in a Se atmosphere. The achievement of cell efficiencies up to 8.6% under AM1.5G (cell area 0.25 cm(2)) and without antireflecting coating indicates that this method can compete with other vacuum-based or more complex wet deposition methods.

The Passive Film on Iron at pH 1–14 A Potential‐Modulated Reflectance Study

The passive film on iron has been studied by potential-modulated reflectance (PMR) spectroscopy over a wide range of pH (1-14) and polarization potentials

Chemistry of Tin Monosulfide ( δ-SnS ) Electrodeposition Effects of pH and Temperature with Tartaric Acid

The conditions of formation of a tin sulfide 8-SnS phase by galvanostatic deposition with tartaric acid were investigated, changing parameters such as pH (1.5 and 2.5) and temperature (50, 70, and 90°C). Uniform films were deposited at both pHs. Cyclic voltammetry data suggested that tin-tartrate complexes were crucial to film electrodeposition and also indicated reduction of sulfur species rather than tin. X-ray diffraction showed the 8-SnS structure to be a pure phase over the range of deposition temperatures (50-90°C) at pH 2.5. This observation was limited to 70°C for films deposited at pH 1.5. Impurities of Sn and α-SnS were found in films deposited at pH 1.5 and temperatures of 50 and 90°C, respectively, indicating that the α-SnS phase is more likely to be formed at lower pHs. All the films annealed at 350°C displayed the α-SnS phase. Scanning electron microscopy showed deposited particles increased in size and became more platelike with increasing temperatures of electrodeposition, but did not change morphology with annealing. UV/vis spectrometry confirmed increased disorder in films deposited at 50°C and a direct allowed optical bandgap of lower energy for the 8-SnS phase compared to that of α-SnS.

The Nickel Electrode: A Potential‐Modulated Reflectance Study

The passive and transpassive films on a Ni electrode have been studied by UV‐visible potential‐modulated reflectance (PMR) spectroscopy over a wide range of pH—1–14—and polarization potentials. PMR is a very sensitive in situ technique, although an established interpretation theory is still lacking for the results obtained with anodic oxide films. Here we follow the criterion that the PMR maxima of the films correspond to absorption edges of compounds present in them. The PMR results indicate that is present in the passive and transpassive film, both in acid and alkaline media. Two higher Ni oxides are also present in the transpassive film in alkaline media, but they could not be identified, owing to the existing confusion about bulk Ni higher oxides.

Efficient Cu2ZnSnS4 solar cells spray coated from a hydro-alcoholic colloid synthesized by instantaneous reaction

Efficient copper zinc tin sulphide (Cu2ZnSnS4) thin film photovoltaic devices were fabricated with a new, fast, and simple preparation method using environmentally friendly solvents. Our process is based upon a versatile and instantaneous synthesis of a Cu–Zn–Sn–S colloid. Dispersing this colloid in a mixture of water (90%) and ethanol (10%), spraying it, and annealing sequentially the samples in two different gases allowed us to grow large grain, crystalline layers of promising photovoltaic quality. We measured cell efficiencies up to 5.0% under simulated AM1.5G (cell area 0.25 cm2). To the best of our knowledge, this is the highest reported efficiency reached with Cu2ZnSnS4 using a spray deposition technique with innocuous solvents.

An in-situ spectroscopic study of the anodic oxide film on a cobalt electrode at pH 4–14 by potential-modulated reflectance

Abstract The anodic oxide film on a Co electrode has been studied by UV-visible potential-modulated reflectance (PMR) over a wide range of pHs (4–14) and polarization potentials. PMR is a very sensitive in-situ technique, but the interpretation of the PMR spectra of anodic oxide films is not complete. Here we follow the criterion that the PMR maxima of the films correspond to optical absorption edges of compounds present in them. According to the PMR results, the film composition is similar in both weakly (pH 9.2) and strongly (pH 13–14) alkaline media. Only some of the observed PMR maxima could be assigned, owing to the lack of spectroscopic data of Co bulk oxides, but additional conclusions were obtained by comparing PMR and voltammetric results.

Unexpected Performances of Flat Sb2S3-Based Hybrid Extremely Thin Absorber Solar Cells

We report unexpected results obtained on hybrid extremely thin absorber (ETA) solar cells based on the structure TiO2/Sb2S3/poly(3-hexylthiophene)/hole conducting layer (HCL). We show that we can maintain a large, state-of-the-art short-circuit current by switching from a three-dimensional to a two-dimensional device, that is, by simplifying drastically the device structure. Moreover, we prove that the HCL plays an important role in the solar cell working mechanism, and influences significantly its open-circuit voltage. We believe that these findings suggest new directions for the optimization of solid-state sensitized solar cells.