Alain Jacob

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.

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.

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.

Strong Reduction of Thermal Conductivity and Enhanced Thermoelectric Properties in CoSbS1-xSex Paracostibite

In order to reduce the thermal conductivity of CoSbS, a newly developed thermoelectric semiconductor, we have aimed at intentionally induce atomic disorder in its structure. This endeavor was guided by Density Functional Theory(DFT) calculations which indicated that substituting sulfur with selenium might be easily achievable experimentally because of the low formation energy of this point defect. Thereby, CoSbS1−xSex compounds having 0 ≤ x ≤ 1 have been synthesized by solid state reaction. Besides the expected semiconducting paracostibite phase, we have observed the appearance of a semimetallic costibite phase, never reported experimentally before. This cross-fertilized theoretical and experimental approach allowed us to reduce by 50% the thermal conductivity of paracostibite and therefore reach a maximum zT of 0.62 at 730 K. This makes this entirely new CoSbS1−xSex alloy very attractive for further optimizations and potential usage in thermoelectric applications.