Bismuth sulfide is a non-toxic, n type semiconductor popular for its use in photoconductive appliances. It has a band gap energy value of 1.3 eV. Bismuth sulfide is a good light absorber, because its coefficient of absorption is high (about 104-105 cm-1). It has good electrical and optoelectronic properties, which is why it is suitable for use in solar cells, photo optic appliances and many more [1].
In this research, we determine the optimal bismuth sulfide synthesis conditions. Distilled water and analytically pure reagents were used to prepare reaction solutions. The temperature for each one of these reactions was 80 °C:
1) 0.1 mol·dm-3 Bi(NO3)3·5H2O mixed with 1 mol·dm-3 SC(NH2)2;
2) 0.1 mol·dm-3 Bi(NO3)3·5H2O mixed with 1 mol·dm-3 SC(NH2)2 with an added oxidizing agent (NH4)2S2O8;
3) 0.1 mol·dm-3 Bi(NO3)3·5H2O mixed with 1 mol·dm-3 SC(NH2)2 with added basic buffer solution;
4) 0.1 mol·dm-3 Bi(NO3)3·5H2O mixed with 1 mol·dm-3 SC(NH2)2 with an added oxidizing agent (NH4)2S2O8 and a basic buffer solution.
Black precipitate of bismuth sulfide was present after every reaction and washed with acetone and distilled water.
All samples were analyzed by X-ray diffraction analysis on the Bruker D8 Advance diffractometer. Precipitate was scanned over the range $2\theta$ = 3-70° at a scanning speed of 1° min-1 using a coupled two theta/theta scan type. This test determined structural characterization of the obtained materials. After an XRD analysis, it was clear that the most precise match with Bi2S3 standard structure was obtained from the first reaction with no oxidizing agent and no basic buffer solution, hence the deposition on FTO glass was made using the first solution and its precipitate.