FAPbI₃ perovskite thin film having α/δ phase junction and its light harvesting performance in solar cell

Abstract

In this study, FAPbI₃ perovskite thin films having α/δ phase junction have been prepared by the two-step solution method at short annealing time. In first stage, the structural, morphological and optical properties of the PbI₂ and FAPbI₃ films have been investigated. The XRD, SEM and UV–Visible analyses have shown that the FAPbI₃ film quality has improved with increasing annealing temperature and the film annealed at 170 °C have bandgap of 1.49 eV and high covering capability with average grain size of ~ 61 nm. The transition from PbI₂ to FAPbI₃ form has enhanced with increasing annealing temperature. Moreover, the α/δ phase junction form crystalline depend annealing temperature has been observed in FAPbI₃ films and the α/δ phase junction has enhanced with increasing annealing temperature. In second stage, performance of the FAPbI₃ films have been investigated as active layer in solar cell having structure of Glass/ITOPEDOT:PSS(~ 50 nm)/FAPbI₃(~ 400 nm)/PC₆₁BM(~ 70 nm)/Al(~ 100 nm). The best solar cell has performance parameters; J_sc is 18.12 mA/cm², V_oc is 0.74 V, FF is 59% and PCE is 7.91%. The results showed that presence of dominant δ phase in FAPbI₃-based solar cells has caused S-sharped J–V character.