K.G. Deepa

SnS quantum dot solar cells with Cu 2 S as counter electrode

Different size SnS quantum dots are prepared by chemical bath deposition. size of the particles are varied from 2.4 to 14.4 nm by varying the deposition time from 30 to 120 min. solar cells are fabricated with these quantum dots. Cu2S coated FTO is used as counter electrode instead of the conventional platinum electrode and Na2S as electrolyte. Cu2S acts as a good catalyst for the polysulfide electrolyte. on comparing with a cell having platinum counter electrode and iodine based electrolyte, Cu2S -polysulfide combination found to improve both the short circuit current and fill factor of the solar cell.

Effect of sulphur variation in AgInS 2 thin films prepared by chemical spray pyrolysis

AgInS₂ thin films are deposited by chemical spray pyrolysis technique. Aqueous solution of Silver Nitrate (AgNO₃), Indium Chloride (InCl₃), and Thiourea (CS (NH₂)₂) are used as the precursors and substrate temperature is kept at 3500C. Effect of variation in sulfur concentration was studied by varying the [S_2-]/ [In³⁺] ratio. Orthorhombic structured AgInS₂ with preferred orientation along (0 0 2) plane is identified using XRD. Even though the crystallinity decreased with increase in sulfur concentration, Ag₂O₃ phase which was observed in the sulfur poor sample was found to be disappeared for higher Sulfur concentration. EDAX data revealed nearly stoichiometric films for [S_2-]/ [In³⁺] ratio 5, with atomic percentage of 26.69, 23.80, 49.81 for Ag, In, S respectively. SEM images show a gradual change from non-spherical to spherical grains with increase in sulfur concentration. Band gap measured was in the range 1.85 to 2.03 eV.