Low-temperature crystallization of piece-pure α-formamidinium lead iodide enabled by evaluate

Even supposing diverse fabrication approaches exist, two-step deposition is one among the most indispensable experimental tactics now feeble to produce efficient, stable PSCs, namely on the industrial scale. The process entails first depositing lead iodide (PbI2) after which adding halide salts of monovalent cations similar to methylammonium iodide (MAI) and formamidinium iodide (FAI) to transform it to perovskite.

Whereas this two-step deposition is higher than other solutions, it is complex to wait on reproducible excessive performance and prolonged-term balance when scaling up, largely this skill that of an absence of administration over the fabrication process. Gaining an determining of the mechanism slack halide perovskite crystallization on the atomic stage is therefore indispensable.

In the paper “A mixed molecular dynamics and experimental evaluate of two-step process enabling low-temperature formation of piece-pure α-FAPbI3,” the authors selected to look at, to this cease, the two-step fabrication of methylammonium lead iodide (MAPbI3) and formamidinium lead iodide (FAPbI3).

Whereas the feeble is a properly-studied plot, the latter used to be chosen this skill that of sexy aspects including a ∼1.45-eV bandgap, excessive-rate provider mobility, and superior thermal balance that appear in its α-FAPbI3 polymorph. The declare with this perovskite however is that the α piece is metastable and the thermodynamic piece transition requires excessive temperatures of spherical 150 levels Celsius. The mixed experimental and theoretical evaluate, printed in the April 23 concern of Science Advances, uncovered the little particulars of the crystallization process, leading the skill to the invention of a low-temperature pathway to the fabrication of the subject cloth.

Whereas old experimental be taught on MAPbI3 printed that the two-step process occurs through intercalation of the MA+ cations in PbI2 layers adopted by a change to the perovskite structure through intermediate phases, the experiments couldn’t get to the underside of the character of these intermediate phases or clarify the underlying atomistic mechanism. The advise of a molecular dynamics (MD) investigation in accordance with an enhanced sampling components called metadynamics (WTMetaD), the team found out that that transformation takes location through a sequence of intermediates. The theoretical results had been in accordance with experiments, encouraging the researchers to analyze whether a identical process used to be also slack the transformation of α-FAPbI3. Initiating from simulations, they realized that a two-step process is indeed doable at lower temperatures in this field cloth. A sequence of in situ X-ray and skinny-movie experiments then confirmed this result and enabled the low-temperature formation of piece-pure α -FAPbI3 skinny films.

Supplied by
Nationwide Centre of Competence in Be taught (NCCR) MARVEL