Sequential Chemical Vapor Deposition of Two-Dimensional Sn–Pb Compound Perovskite Thin Films and Its Exciton Transport

Sequential low-pressure chemical vapor deposition (CVD) offers a controllable and scalable route for the conformal growth of Pb-based perovskite materials, with an improved environmental stability and control of the phase stability of the material. Reducing the dimensionality of the material and alloying with Sn have the additional benefit of mitigating both the instability and environmental challenges associated with Pb. Herein, we report on the sequential CVD of a two-dimensional (2D) Sn–Pb mixed-halide perovskite compound by converting a SnCl2/PbCl2 precursor in a phenylethylamine iodide (PEAI) atmosphere from 80 to 120 °C. A conversion temperature of 100 °C is optimal for the growth of a highly crystalline, uniform, and compact 2D Pb–Sn compound perovskite layer with well-defined grains up to 5 μm, consistent with its optical absorbance and emission properties. Simultaneously, a crystalline PbI2 layer is produced and attributed to the interruption of the intercalation process. Temperature-dependent photoluminescence measurements show a single excitonic peak from 20 to 360 K for both 2D Sn-only and Sn–Pb compound films, highlighting the phase stability of the material. The observed excitonic peak broadening in the compound film is attributed to growth in the defect density accompanied by a weakening of the exciton–phonon interaction caused by Frenkel-like excitons. This work will contribute toward an understanding of the transport properties of CVD-grown 2D perovskites that will develop the capability of producing 2D-layered field-effect transistors and solar cells.