Inkjet Printing Epitaxial Metal Halide Perovskites on Various Substrates?

In their Progress Report, Sytnyk et al. claimed the epitaxial deposition of metal halide perovskites by inkjet printing on various substrates. The claims of epitaxy are doubtful due to a lack of convincing experimental evidence. Both optical microscopy and scanning electron microscopy images alone are insufficient to prove epitaxy. Even if the images suggest that epitaxial growth might have been achieved, direct evidences from X-ray diffraction (XRD) or electron diffraction are still needed. Among the six perovskite-substrate systems, only two CH3NH3PbI3 deposits on (111)PbTe/BaF2 are characterized with XRD. According to their XRD patterns, actually, it is estimated that each of their MAPbI(3) deposits contains only <20% epitaxial components and the component of nearly random orientation is predominant besides considerable impurity PbI2. None of the MAPbI(3) deposits can be considered epitaxial. It is critical to point out the errors in the methodology for verifying epitaxy, so that researchers would not be misled by Sytnyk's paper. Importantly, a new methodology to quantify the volume fraction of each epitaxial component in a thin film from XRD measurements is proposed. It is reliable to estimate the degree of texture according to the proposed equations, quite different from using Lotgering degree of orientation.

Automated summary

The study points out the doubts surrounding Sytnyk et al.'s claims of epitaxial deposition of metal halide perovskites by inkjet printing on various substrates, emphasizing that optical microscopy and scanning electron microscopy images alone are insufficient evidence. A new methodology to quantify the volume fraction of each epitaxial component in a thin film from XRD measurements is proposed as a way to address the errors in verifying epitaxy.