Chemically deposited antimony selenide ͑Sb 2 Se 3 ͒ thin film has a coexisting antimony oxide ͑Sb 2 O 3 ͒ phase which may be converted to crystalline Sb 2 Se 3 thin films with an optical bandgap of 1.13 eV when heated at 300°C in nitrogen in the presence of selenium vapor. Instead of this, if the heating is done with an Sb 2 S 3 thin film on the chemically deposited Sb 2 Se 3 :Sb 2 O 3 thin film, a solid solution with the coexisting oxide phase ͑Sb 2 Se 3−x S x :Sb 2 O 3 ͒ is produced. The optical bandgap of such absorber material is 1.34-1.58 eV. The as-deposited thin films as well as those produced by heating are photoconductive. They were incorporated into solar-cell structures developed entirely by chemical deposition on SnO 2 :F-coated commercial transparent conductive oxide ͑TCO͒ glass. The cell structure, TCO/CdS/Sb 2 Se 3 :Sb 2 O 3 /PbS, showed an open-circuit voltage ͑V oc ͒ of 540 mV and short-circuit current density ͑J sc ͒ of 0.67 mA/cm 2 . In the cell TCO/CdS/Sb 2 Se 3−x S x :Sb 2 O 3 /PbS produced by heating in nitrogen, V oc is 520 mV, J sc is 4.2 mA/cm 2 , and conversion efficiency ͑͒ is 0.66%. The scalability of the all-chemically deposited solar cell is demonstrated in four series-connected cells of area 1 cm 2 each, showing short-circuit current of 1.5 mA and V oc of 1.9 V under sunlight.
Utilization of lignocellulosic materials for the production of value-added chemicals or biofuels generally requires a pretreatment process to overcome the recalcitrance of the plant biomass for further enzymatic hydrolysis and fermentation stages. Two of the most employed pretreatment processes are the ones that used dilute acid (DA) and alkaline (AL) catalyst providing specific effects on the physicochemical structure of the biomass, such as high xylan and lignin removal for DA and AL, respectively. Another important effect that need to be studied is the use of a high solids pretreatment (≥15%) since offers many advantaged over lower solids loadings, including increased sugar and ethanol concentrations (in combination with a high solids saccharification), which will be reflected in lower capital costs; however, this data is currently limited. In this study, several variables, such as catalyst loading, retention time, and solids loading, were studied using response surface methodology (RSM) based on a factorial central composite design of DA and AL pretreatment on agave bagasse using a range of solids from 3 to 30% (w/w) to obtain optimal process conditions for each pretreatment. Subsequently enzymatic hydrolysis was performed using Novozymes Cellic CTec2 and HTec2 presented as total reducing sugar (TRS) yield. Pretreated biomass was characterized by wet-chemistry techniques and selected samples were analyzed by calorimetric techniques, and scanning electron/confocal fluorescent microscopy. RSM was also used to optimize the pretreatment conditions for maximum TRS yield. The optimum conditions were determined for AL pretreatment: 1.87% NaOH concentration, 50.3 min and 13.1% solids loading, whereas DA pretreatment: 2.1% acid concentration, 33.8 min and 8.5% solids loading.
Antimony sulfide thin films (thickness, 500 nm) were deposited on chemically deposited CdS thin films (100 nm) obtained on 3 mm glass substrates coated with a transparent conductive coating of SnO2:F (TEC-15 with 15 Ω sheet resistance). Two different chemical formulations were used for depositing antimony sulfide films. These contained (i) antimony trichloride dissolved in acetone and sodium thiosulfate, and (ii) potassium antimony tartrate, triethanolamine, ammonia, thioacetamide and small concentrations of silicotungstic acid. The films were heated at 250 °C in nitrogen. The cell structure was completed by depositing a 200 nm p-type PbS thin film. Graphite paint applied on the PbS thin film and a subsequent layer of silver paint served as the p-side contact. The cell structure: SnO2:F/CdS/Sb2S3 (i or ii)/PbS showed open circuit voltage (Voc) of 640 mV and short circuit current density (Jsc) above 1 mA cm−2 under 1 kW m−2 tungsten–halogen radiation. Four cells, each of 1.7 cm2 area, were series-connected to give Voc of 1.6 V and a short circuit current of 4.1 mA under sunlight (1060 W m−2).
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