Atmospheric annealing effect on TiO2/Sb2S3/P3HT heterojunction hybrid solar cell performance

We investigate the low-cost, earth-abundant and air-stable inorganic absorber Sb2S3 that can be processed in the air for organic-inorganic hybrid solar cell applications. To this end, we deposited thin layers of Sb2S3 with thicknesses of 45.0 +/- 5, 60.0 +/- 7, 80.0 +/- 8, 100.0 +/- 10 and 120 +/- 24 nm by a thermal evaporation method. The absorber Sb2S3 and the hole transporting layer P3HT were annealed under atmospheric conditions at temperatures of 320 and 150 degrees C for 30 and 10 min in air, respectively, to prepare glass/ITO/TiO2/Sb2S3/P3HT/Ag heterojunction solar cells. We noticed that the values of J(sc), V-oc, FF and eta were changed with the thickness variation. It is interesting that the best device condition was obtained for a thickness of 100 +/- 10 nm achieving an efficiency of 1.94% which was the highest efficiency among the flat structure devices. SEM, XRD, Raman and TEM studies showed that the annealed films were polycrystalline in nature. Further characterization was carried out of the best device by spectroscopic ellipsometry, UV-vis, QE, XPS and UPS. In addition, important electronic and optical properties of Sb2S3 were investigated based on first principles density functional theory (DFT) with generalized gradient approximation (GGA). The obtained experimental values of n, k, epsilon(1) and epsilon(2) are close to the theoretical results.