Efficient TiO2 Surface Treatment Using Cs2CO3 for Solution-Processed Planar-Type Sb2S3 Solar Cells

We report a highly effective surface treatment method for planar-type Sb 2 S 3 solar cells by employing a Cs 2 CO 3 -modified compact TiO 2 (c-TiO 2 ) electron transport layer. It is found that surface treatment using a Cs 2 CO 3 solution can shift the work function of c-TiO 2 upward and reduce its surface roughness. As a result, compared with the power conversion efficiency of untreated solar cells, that of the treated solar cells with a glass/FTO/c-TiO 2 (/Cs 2 CO 3 )/Sb 2 S 3 /P3HT/Au structure significantly improved from 2.83 to 3.97%. This study demonstrates that the introduction of Cs 2 CO 3 on a c-TiO 2 layer is a simple and efficient way to adjust the work function of the electron transport layer and fabricate high-performance planar-type Sb 2 S 3 solar cells.