Antimony sulfide and Silver antimony sulfide absorbers for thin film solar cells

Abstract

ABSTRACTThin films of antimony sulfide (Sb2S3) were prepared with different silver-ion content in a chemical deposition bath, and silver antimony sulfide (AgSbS2) was produced through the addition of higher concentrations of silver-ions in the bath. The chemical deposition solution mixture contained antimony trichloride (SbCl3) and sodium thiosulfate (Na2S2O3). For molar ratio, AgNO3:SbCl3, 0.002 – 0.02, XRD patterns of the Sb2S3-Ag films heated at 280 ºC match that of the mineral stibnite (Sb2S3). The optical band gap (Eg) of these films is in the 1.93-1.80 eV range. At higher molar concentrations of Ag, lower is the Eg of the films. Electrical conductivity under illumination (σph) is 7.4x10-5 Ω-1cm-1 for a film with Ag:Sb 0.002 in the bath, which is about three orders of magnitude higher than that of a film prepared without Ag. At Ag:Sb 0.2, the XRD pattern of the heated film shows the presence of Ag3SbS3 and AgSbS2. Single-phase AgSbS2 (cubic miargyrite, a = 0.5652 nm) film is formed for Ag:Sb 0.4 and the film heated at 260 oC. The Eg of the film is 1.75 eV for the Sb2S3/Ag-Sb-S film and 1.68 eV for AgSbS2. Solar cell structures of TCO(SnO2:F)/CdS(200 nm)/Sb2S3(150 nm)/graphite, as well as with Sb2S3-Ag absorbers were developed through sequential chemical deposition. The cells with the colloidal graphite paint on the absorber were heated at 260 ºC for 15 min each. The Voc of the cells are 620-635 mV, with the cell using Sb2S3-Ag (0.004) film showing a Jsc of 2.00 mA/cm2, which is higher than the 1.69 mA/cm2 observed in cells with Sb2S3 absorber. In cells using AgSbS2 absorber, Voc is 490 mV, and Jsc is very low, 0.12 mA/cm2. The present work offers a wider range of absorber materials for thin film and hybrid solar cells.