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

Abstract

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 °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 η 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, ε₁ and ε₂ are close to the theoretical results.