Performance improvement of Sb2S3-sensitized solar cell by introducing hole buffer layer in cobalt complex electrolyte

We found that the insertion of the poly-3-hexylthiophene (P3HT) layer into the pristine device results in great improvement of the efficiency, from 2.0% to 3.3% at 1 sun illumination. The improvement was mainly attributed to the improved fill factor, which for the Sb2S3 sensitized solar cell was seriously degraded from 56.0% (at 0.1 sun) to 31.5% (at 1 sun), whereas the fill factor of the Sb2S3/P3HT sensitized solar cell was only moderately degraded, from 59.3% (at 0.1 sun) to 40.4%. The role of P3HT as a hole buffer layer was analyzed by electrochemical impedance spectroscopy (EIS).