Efficient Nanostructured TiO₂/SnS Heterojunction Solar Cells

Tin sulfide (SnS) is one of the most promising solar cell materials, as it is abundant, environment friendly, available at low cost, and offers long-term stability. However, the highest efficiency of the SnS solar cell reported so far remains at 4.36% even using the expensive atomic layer deposition process. This study reports on the fabrication of SnS solar cells by a solution process that employs rapid thermal treatment for few seconds under Ar gas flow after spin-coating a precursor solution of SnCl₂ and thiourea dissolved in dimethylformamide onto a nanostructured thin TiO₂ electrode. The best-performing cell exhibits power conversion efficiency (PCE) of 3.8% under 1 sun radiation conditions (AM1.5G). Moreover, secondary treatment using SnCl₂ results in a significant improvement of 4.8% in PCE, which is one of the highest efficiencies among SnS-based solar cells, especially with TiO₂ electrodes. The thin film properties of SnS after SnCl₂ secondary treatment are analyzed using grazing-incidence wide-angle X-ray scattering, and high-resolution transmittance electron microscopy.