Antisolvent processing of lead halide perovskite thin films studied by in situ X-ray diffraction

Abstract

The conversion mechanism from the precursor ink to the perovskite film using antisolvent-induced crystallization has been studied using in situ X-ray diffraction during blade coating and antisolvent deposition.

CsI‐Antisolvent Adduct Formation in All‐Inorganic Metal Halide Perovskites

“…To understand the crystallization dynamics and antisolvent mechanism of CsPbI 3 , the as‐quenched films prior to annealing were first studied. It has previously been shown that the formation of a crystalline intermediate, typically light brown, precursor phase is critical in forming high‐quality, pinhole‐free films . Without an antisolvent, the CsPbI 3 as‐quenched, preannealed film retains a yellow color with an absorption onset of 450 nm ( Figure 1 A).…”

“…These antisolvent physical parameters specifically do not account for any sort of adduct formation such as PbI 2 –DMSO, which has been identified to strongly influence the crystallization dynamics in halide perovskites . Basicity scales like the Gutmann's donor notionally account for the strength of adduct formation, but is based on adduct formation with a model Lewis acid (SbCl 5 ) and does not account for hardness or softness of the constituents thus is incomplete .…”

“…It has previously been shown that the formation of a crystalline intermediate, typically light brown, precursor phase is critical in forming high-quality, pinhole-free films. [15,38] Without an antisolvent, the CsPbI 3 as-quenched, preannealed film retains a yellow color with an absorption onset of 450 nm (Figure 1A). CB, Tol, and DEE do not change the asquenched film from the yellow color ( Figure 1C).…”

“…An antisolvent quench is also incorporated to intentionally control the exact nucleation time through the introduction of an antisolvent that supersaturates the precursor solution and removes excess precursor solvent . The antisolvent quench must happen within a specific nucleation window since quenching too early will not cause supersaturation and quenching after the film has already begun to nucleate will not induce the ideal nucleation site density . When the quenching occurs within this window, heterogeneous nucleation is promoted at the initial crystallization stage and minimizes pinholes in the resulting films .…”

“…[5,[12][13][14] The antisolvent quench must happen within a specific nucleation window since quenching too early will not cause supersaturation and quenching after the film has already begun to nucleate will not induce the ideal nucleation site density. [15][16][17] When the quenching occurs within this window, heterogeneous nucleation is promoted at the initial crystallization stage and minimizes pinholes in the resulting films. [9,13] By controlling nucleation and slowing down the crystallization, the perovskite films have more uniform film coverage.…”