Origin of Ionic Inhomogeneity in MAPb(IxBr1-x)3Perovskite Thin Films Revealed by In-Situ Spectroscopy during Spin Coating and Annealing

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Abstract

Irradiation-induced phase segregation in mixed methylammonium halide perovskite samples such as methylammonium lead bromide-iodide, MAPb(IxBr1-x)3, is being studied intensively because it limits the efficiency of wide band gap perovskite solar cells. It has been postulated that this phenomenon depends on the intrinsic ionic (in)homogeneity in samples already induced during film formation. A deeper understanding of the MAPb(IxBr1-x)3 formation processes and the influence of the halide ratio, solvents, and the perovskite precursor composition as well as the influence of processing parameters during deposition, e.g., spin coating and annealing parameters, is still lacking. Here, we use a fiber optic-based optical in-situ setup to study the formation processes of the MAPb(IxBr1-x)3 series on a subsecond time scale during spin coating and thermal annealing. In-situ UV-vis measurements during spin coating reveal the influence of different halide ratios, x, in the precursor solution on the preferential crystallization of the phase. Pure bromide samples directly form a perovskite phase, samples with high iodide content form a solvate intermediate phase, and samples with a mixed stoichiometry between 0.1 ≤ x ≤ 0.6 form both. This leads to a heterogeneous formation process via two competing reaction pathways, that leads to a heterogeneous mixture of phases, during spin coating and rationalizes the compositional heterogeneity of mixed bromide-iodide samples even after annealing.

Detaljer

Författare
Enheter & grupper
Externa organisationer
  • Helmholtz-Zentrum Berlin for Materials and Energy
  • Humboldt University of Berlin
Forskningsområden

Ämnesklassifikation (UKÄ) – OBLIGATORISK

  • Kemi

Nyckelord

Originalspråkengelska
Sidor (från-till)30343-30352
Antal sidor10
TidskriftACS Applied Materials and Interfaces
Volym12
Utgåva nummer27
StatusPublished - 2020 jul 8
PublikationskategoriForskning
Peer review utfördJa