Understanding the Formation Process of Perovskite Layers Grown by Chemical Vapour Deposition

Abstract

This work aims at extending the understanding of the formation processes of (Cs0.07FA0.93)PbI3 perovskite layers deposited by a two-step vapour method. In a first step, an inorganic CsI/PbI2 precursor stack is deposited by thermal evaporation (TE). A chemical vapour deposition (CVD) is then used to convert the precursor into the perovskite layer by reaction with a chemical vapour of formamidinium iodide (FAI). Here we show how crystallinity and morphology of the TE precursor layer are both influenced not only by the substrate surface properties but also by the thermal treatment in the initial phase of the CVD process. Furthermore, we provide insights on the evolution of perovskite film formation and show how a uniform elemental composition is achieved by the diffusion of cesium through PbI2 during the CVD conversion reaction.

Hydrothermal Growth and Orientation of LaFeO3 Epitaxial Films

“…The thickness of the LaFeO 3 film obtained at the reaction time of 2 h is about 2 μm, as shown in Figure 8 b. The thickness of the films prepared by the hydrothermal method is significantly greater compared to those obtained via other epitaxial methods [ 19 , 20 , 22 ]. To obtain thinner films using the hydrothermal method, a lower reaction temperature and extension reaction are required.…”

“…LaFeO 3 thin films are an important class of functional materials because of their structural stability and unique electromagnetic, catalytic, and gas-sensitive properties [ 15 , 16 , 17 , 18 ]. A variety of methods, such as pulsed-laser deposition (PLD) [ 19 ], molecular-beam epitaxy (MBE) [ 20 ], reductive annealing [ 21 ], and chemical vapor deposition (CVD) [ 22 ], have been applied to prepare epitaxial thin films. Compared to these methods for preparing epitaxial films, the one-step hydrothermal preparation of epitaxial films has the advantages of mild conditions, a lower preparation cost, and a simple procedure, so it is an attractive alternative method to the abovementioned costly techniques [ 23 , 24 ].…”

Substoichiometric Mixing of Metal Halide Powders and Their Single-Source Evaporation for Perovskite Photovoltaics

“…Investigating the spatial distribution of chemical species after single-source evaporation is out of the scope of this study. However, the work of Moser et al 26 shows that upon conversion into perovskite of a metal halide template, compositional gradients are homogenized. In their case, the initial template consisted of a bilayer of a pure PbI 2 layer on top of a pure CsI layer, and after conversion into a perovskite, Cs and Pb are homogeneously spread along the perovskite layer.…”