A versatile lead iodide particle synthesis and film surface analysis for optoelectronics

Lead (II) iodide, PbI2, semiconductor was synthesized using versatile methods such as hydrothermal, refluxing, solid-state reaction, and co-precipitation for optoelectronics. All the PbI2 particles exhibited hexagonal-layered 2H structure in which the average crystallite size and optical bandgap (E-g) were 57 +/- 10 nm and 2.31 eV, respectively. Then, PbI2 films were prepared using dimethyl sulfoxide (DMSO) or dimethylformamide (DMF) on the top of a mesoporous TiO2 layer, yielding a wider E-g of 2.33-2.36. Finally, through water contact angle measurement, the surface and interfacial properties of the thin film were characterized, exhibiting initial solid-vapor surface tension (gamma(sv)) of 6.1-6.4 mJ/m(2) and solubility parameter (delta) of 4.51-4.62 (cal/cm(3))(1/2). However, when these PbI2 films were exposed to H2O molecules in air, delta changes from 4.62 to 7.28 (cal/cm(3))(1/2 )for PbI2 (DMSO) film or 4.51 to 12.98 (cal/cm(3))(1/2 )for the PbI2 (DMF) film, respectively. Finally, by employing the theory of melting point depression combined with the Flory-Huggins lattice theory, the interfacial interactions between PbI2 and regioregular poly (3-hexylthiophene-2,5-diyl) were qualitatively characterized. The smaller the chi interaction parameter, the more depressed the melting point. (C) 2020 Elsevier B.V. All rights reserved.