Manipulation of facet orientation in hybrid perovskite polycrystalline films by cation cascade

Abstract

Crystal orientations in multiple orders correlate to the properties of polycrystalline materials, and it is critical to manipulate these microstructural arrangements to enhance device performance. Herein, we report a controllable approach to manipulate the facet orientation within the ABX3 hybrid perovskites polycrystalline films by cation cascade doping at A-site. Two-dimensional synchrotron radiation grazing incidence wide-angle X-ray scattering is employed to probe the crystal orientations in multiple orders in mixed perovskites thin films, revealing a general pattern to guide crystal planes stacking upon extrinsic doping during crystallization. Different from previous studies, this method enables to adjust the crystal stacking mode of certain crystallographic planes in polycrystalline perovskites. Moreover, the preferred facet orientation is found to facilitate photocarrier transport across the absorber and pertaining interface in the resultant PV device, which provides an exemplary paradigm for further explorations that relate to the microstructures of hybrid perovskite materials and relevant optoelectronics.

In Situ Observation of Crystallization Dynamics and Grain Orientation in Sequential Deposition of Metal Halide Perovskites

“…Previous reports show that the formation of the perovskite polycrystalline films involves the formation of [PbI 6 ] 4− polyiodides as intermediates followed by the further nucleation and growth processes . The arrangement of the [PbI 6 ] 4− octahedrons could intimately determine the crystal facet orientations in the film, which is associated with the overall chemical potential of the system and the formation energy of the final product . At low temperatures, the α‐FAPbI 3 species possesses the preferable orientation with the {100} planes parallel to the substrate, which could be due to the formation of the horizontally aligned [PbI 6 ] 4− slabs dictated by the stacking pattern of PbI 2 .…”

“…Previous studies draw much attention on film morphologies, such as crystal sizes, grain boundaries, and pinholes, whereas the evolution of crystal microstructures during perovskite formation has not been fully surveyed in the sequential deposition of FAPbI 3 . Recent reports reveal that the control of crystal orientations in a single‐grain scale could effectively alter the resultant device efficiency due to the facet‐dependent optoelectronic characters . Accordingly, crystal facet orientation management in the sequential deposition of FAPbI 3 could provide another knob to fine tune the film quality.…”

Emerging Conductive Atomic Force Microscopy for Metal Halide Perovskite Materials and Solar Cells

“…Alkali elements (Cs, Rb, and K) were incorporated to form cation cascade doping FAMA (formamidinium/methylammonium)‐mixed perovskite. The alkali elements doping can manipulate the facet orientation of perovskite grains, which further affect the charge transport performance . As presented in Figure 14 a, with appropriate concentration of Cs, the azimuth angle shifted from the original 40.56° to 30.18°.…”

“…a) The crystal stacking patterns, b) wide‐angle X‐ray scattering analysis and c) C‐AFM images of FAMA‐, FAMAC‐, FAMACsRb‐, and FAMACsRbK‐based perovskites films. Reproduced with permission . Copyright 2018, Nature Publishing Group…”

Unveiling the Nanoparticle‐Seeded Catalytic Nucleation Kinetics of Perovskite Solar Cells by Time‐Resolved GIXS

“…Improved thermal stability with weaker decay of the peak intensity of the perovskite crystals at elevated annealing temperature was also observed for the PbS NC‐seeded perovskite thin film, as compared to that in the pristine perovskite thin film (Figure S8, Supporting Information). The enhanced thermal stability of the perovskite crystals through lattice anchoring to the PbS NCs reported here would be of particular advantages in considerably long high‐temperature annealing for the cubic α‐phase of the high‐performance perovskite solar cells with mixed cations of Cs + , CH(NH 2 ) 2 + (FA), and MA + . The photoactive α phase of FA x MA 1− x PbI 3 is known to transit relatively easily to the photoinactive yellow orthorhombic δ phase at room temperature .…”