Inkjet Printing Epitaxial Metal Halide Perovskites on Various Substrates?

Abstract

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 MAPbI3 deposits contains only <20% epitaxial components and the component of nearly random orientation is predominant besides considerable impurity PbI2. None of the MAPbI3 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.

Epitaxial Growth of Quasi-intrinsic CsPbBr3 Film on a SrTiO3 Substrate by Pulsed Laser Deposition

“…The epitaxial growth of the archetypical perovskites (CH 3 NH 3 PbBr 3 /I 3 , CsPbBr 3 /Cl 3 ) using a cheaper single-nozzle inkjet printer was reported by Heiss et al, and they claimed that single-crystal micro/nanostructure arrays and crystal coherent films have been obtained on the selected substrate . But Lu et al commented that the epitaxy claimed by Kelso and Heiss is doubtful, because images of optical microscope and scanning electron microscope are not enough to prove the epitaxy. , Up to now, the liquid-phase epitaxy of perovskite films is still controversial, as it is difficult to control the homogeneity of doping and multicompound combinations during the growth process.…”

Critical evaluation of (110) texture in lithium electrodeposits on isotropic Cu polycrystals

“…Therefore, it is totally wrong to quantify (110) texture with the intensity fraction . As we know, it is unreliable and incorrect to make any quantitative assessment of (110) texture with the Lotgering degree of orientation 9 – 11 Such indiscriminate assessments give usually an overestimated value of texture 4 – 6 , 9 . Quantifying (110) texture with the is even stray farther away, see Table 1 .…”

“…Here, ΔΩ w ≈ π Δ ψ Δ ω /4, where Δ ψ and Δ ω in unit of radian are the diameters of angle window parallel and perpendicular to the diffraction plane, respectively 12 , 13 . If the ΔΩ w covered the tilt spread ΔΩ of (110) texture, the f v (110) values of the Li electrodeposits could be roughly estimated from the intensity ratio of the 110 peak to a nearby peak hkl 11 . In order to balance the intensity fluctuation of weak 200 and 211 peaks, their total intensity is chosen to represent the diffraction contributions from the randomly oriented Li component.…”