Thin films of microcrystalline (CH3NH3)(C6H5C2H4NH3)2Pb2Br7 and related compounds: fabrication and optical properties

Abstract Thin films of microcrystalline (CH 3 NH 3 )(C 6 H 5 C 2 H 4 NH 3 ) 2 Pb 2 Br 7 and related compounds were prepared by the spin-coating method from their DMF solutions. It was essential to use precursor solutions dissolved with excess amount of CH 3 NH 3 Br for preparing (CH 3 NH 3 )(C 6 H 5 C 2 H 4 NH 3 ) 2 Pb 2 Br 7 film. The substrate surface temperature and coating atmosphere also affected the thin film formation. (CH 3 NH 3 ) m −1 (C 6 H 5 C 2 H 4 NH 3 ) 2 Pb m Br 3 m + 1 ( m = 1, 2 and ∞) films showed clear exciton absorption and free exciton emission at room temperature due to their large exciton binding energy. The unknown film synthesized here showed no exciton band; however, this film exhibited clear blue-green emission from the band edge.