Structural and compositional characteristics of vacuum deposited methylammonium lead halide perovskite layers in dependence on background pressure and substrate temperature.

In a physical vapor deposition process for fabrication of perovskite absorber layers it is an important prerequisite for large scale application to understand the reaction steps and the impact of the deposition parameters on the structural and compositional characteristics of vacuum deposited lead halide perovskite layers. In the sequential deposition method, we found a narrow and low lying temperature window for the transformation of a vapor deposited PbCl 2 base layer to CH 3 NH 3 PbI 3 perovskite by reaction with evaporated CH 3 NH 3 I. To modify the deposition parameter window, we systematically varied background pressure and substrate temperature and analyzed the resulting composition using X-ray diffraction, energy-dispersive X-ray spectroscopy, and scanning electron microscopy. The resulting reaction products and byproducts CH 3 NH 3 PbI 3 , CH 3 NH 3 PbCl 3 , PbICl, PbCl 2 , and PbI 2 were identified and the variation of their concentration in dependence of background pressure and substrate temperature is explained by discussion of a set of reaction equations and reaction mechanisms on a thermodynamic basis. [ABSTRACT FROM AUTHOR]