Vacuum evaporated CsPbX3 (X=Cl, Br, I) thin films: optical and transport properties

Thin films of ternary CsPbX3 compounds were prepared by vacuum co-evaporation of CsX and PbX2 purified powders. Bridgman-grown crystals of the ternary CsPbX3 phases were also evaporated to produce “bulk-like” (BE) thin films. The films are constituted by nanocrystallites as evidenced by X-ray diffraction (XRD) and Atomic Force Microscopy (AFM). Electrical characterization reveals a complex response of the materials either on the applied voltage or temperature variations. I(V) curves are ohmic for low voltages while an exponential increase is observed over 80 V, which supports a field-assisted emission contribution to the dark current. Degenerate scattering mechanisms control the carriers transport at the lower temperatures while activate conduction with energy barrier lower than one half the band gap takes place for temperatures greater than 300 K in all deposited materials. A model is proposed to discuss the experimental results.