Synthesis and characterization of perovskite FAPbBr3−x I x thin films for solar cells

FAPbI3, FAPbBr3, and FAPbBr3−xIx perovskite thin films were produced in a single step from a solution containing a mixture of FAI, PbI2, FABr, and PbBr2 (FA = formamidinium). FAPbBr3−xIx perovskite thin films were deposited onto ITO-coated glass substrates by spin coating. X-ray diffraction analyses confirmed that these thin-film perovskites crystallize in the cubic phase (Pm-3 m) for all composition range 0 ≤ x ≤ 3. Mixed lead perovskites showed a high absorbance in the UV–Vis range. The optical band gap was estimated from spectral absorbance measurements. It was found that the onset of the absorption edge for FAPbBr3–xIx thin films ranges between 1.47 and 2.20 eV for x = 0 and x = 3, respectively. Photoluminescence emission energies for mixed halide perovskites were also dependent on their composition and presented intermediate values from 810.4 nm for FAPbI3 to 547.3 nm for FAPbBr3. Graphical abstract