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

Thin films of microcrystalline (CH3NH3)(C6H5C2H4NH3)2Pb2Br7 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 CH3NH3Br for preparing (CH3NH3)(C6H5C2H4NH3)2Pb2Br7 film. The substrate surface temperature and coating atmosphere also affected the thin film formation. (CH3NH3)m−1(C6H5C2H4NH3)2PbmBr3m + 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.