TiO2Sensitization with Bi2S3Quantum Dots: The Inconvenience of Sodium Ions in the Deposition Procedure

This paper highlights the inconvenience of sodium ions in the Bi 2 S 3 quantum dots (QDs) deposition procedure, on the TiO 2 surface, for the conversion efficiency of the sensitized solar cells derived from these materials. Porous TiO 2 electrodes were sensitized with QDs obtained by the successive ion layer adsorption and reaction (SILAR) technique, using aqueous solutions of Bi(NO 3 ) 3 as the cation precursor and Na 2 S as the sulfide source. Independently, elemental sulfur vapor was used to replace the Na 2 S solution in the synthesis procedure. The obtained layers were characterized by X-ray diffraction, transmission electron microscopy, Raman scattering, and diffuse reflectance spectroscopy. We found that the presence of sodium ions in the reaction system strongly affects the formation of Bi 2 S 3 on the porous TiO 2 . This result contrasts with what other authors have claimed. Using elemental sulfur vapor as a precursor, crystalline Bi 2 S 3 nanoparticles are formed on the TiO 2 surface. The sensitized solar cells produced using the two different types of photoelectrodes were compared based on the photocurrent–voltage characteristic and the photocurrent time stability. The sensitized photoelectrodes derived from elemental sulfur vapor are much more stable over time and can achieve an efficiency of 0.84%. This is the highest conversion efficiency value for any Bi 2 S 3 photoelectrochemical cell.