Precise Control of Perovskite Crystallization Kinetics via Sequential A-Site Doping.
basic_science · Level V
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- Record sourced from PubMed, PMID 32939914.
- Also identified by DOI 10.1002/adma.202004630.
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Abstract
Two-step-fabricated FAPbI<sub>3</sub> -based perovskites have attracted increasing attention because of their excellent film quality and reproducibility. However, the underlying film formation mechanism remains mysterious. Here, the crystallization kinetics of a benchmark FAPbI<sub>3</sub> -based perovskite film with sequential A-site doping of Cs<sup>+</sup> and GA<sup>+</sup> is revealed by in situ X-ray scattering and first-principles calculations. Incorporating Cs<sup>+</sup> in the first step induces an alternative pathway from δ-CsPbI<sub>3</sub> to perovskite α-phase, which is energetically more favorable than the conventional pathways from PbI<sub>2</sub> . However, pinholes are formed due to the nonuniform nucleation with sparse δ-CsPbI<sub>3</sub> crystals. Fortunately, incorporating GA<sup>+</sup> in the second step can not only promote the phase transition from δ-CsPbI<sub>3</sub> to the perovskite α-phase, but also eliminate pinholes via Ostwald ripening and enhanced grain boundary migration, thus boosting efficiencies of perovskite solar cells over 23%. This work demonstrates the unprecedented advantage of the two-step process over the one-step process, allowing a precise control of the perovskite crystallization kinetics by decoupling the crystal nucleation and growth process.