Title: Film formation mechanisms in mixed-dimensional 2D/3D halide perovskite films revealed by in situ grazing-incidence wide-angle X-ray scattering

Abstract

We report mixed dimensionality 2D/3D hybrid halide perovskites retain the stability of 2D perovskites (formula (A')2(A)n-1PbnI3n+1) and long diffusion lengths of the 3D materials (formula AMX3), thereby affording solar cells with extended stability as well as state of the art efficiencies approaching that of the 3D materials. These films are made by spin coating precursor solutions with arbitrarily large average layer thickness n ($$\langle$$n$$\rangle$$ > 7) to give films with both 2D and 3D phases present. While the 2D and 3D perovskite film formation mechanisms have been studied previously, little is understood about composite 2D/3D film formation. We used in situ grazing-incidence wide-angle scattering (GIWAXS) with synchrotron radiation to fully characterize films fabricated from precursor solutions with stoichiometries of (BA)₂(MA)_n-1Pb_nI_3n+1 ($$\langle$$n$$\rangle$$ = 3, 4, 5, 7, “12,” “50,” and ∞ (MAPbI₃)). Four different mechanisms are seen depending on the stoichiometry in the precursor solution. When $$\langle$$n$$\rangle$$ = 3, oriented perovskite grows directly. For $$\langle$$n$$\rangle$$ = 4-5, the needle-shaped solvate (MA)₂Pb₃I₈·2DMF forms concomitantly with the oriented perovskite which leads to 2D/3D composite films. For $$\langle$$n$$\rangle$$ ≥ 7, this solvate dominates and unoriented perovskite grows in secondarily. For 3D perovskite, the solvate is the only phase formed. Kinetic analysis shows faster and earlier growth of the solvate with increasing $$\langle$$n$$\rangle$$. Using this knowledge, we show that the undesirable solvate mechanism can be reduced by addition of excess ammonium iodide in the precursor solution to give highly oriented films.

Authors:

Hoffman, Justin M. ^[1]; Hadar, Ido ^[1]; Li, Xiaotong ^[1]; Ke, Weijun ^[1]; Vasileiadou, Eugenia S. ^[1]; Strzalka, Joseph ^[2]; Chen, Lin X. ^[3]; Kanatzidis, Mercouri G. ^[1]

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+ Show Author Affiliations

1. Northwestern Univ., Evanston, IL (United States)
2. Argonne National Lab. (ANL), Argonne, IL (United States)
3. Northwestern Univ., Evanston, IL (United States); Argonne National Lab. (ANL), Argonne, IL (United States)

Publication Date:

Thu Apr 14 00:00:00 EDT 2022

Research Org.:

Argonne National Lab. (ANL), Argonne, IL (United States)

Sponsoring Org.:

USDOE Office of Science (SC); US Department of the Navy, Office of Naval Research (ONR); Air Force Research Laboratory (AFRL); US Army Research Office (ARO); National Science Foundation (NSF); State of Illinois; Northwestern University

OSTI Identifier:

1866390

Grant/Contract Number:  

AC02-06CH11357; N00014-20-1-2725; ECCS-1542205; DMR-1720139

Resource Type:

Accepted Manuscript

Journal Name:

Chem

Additional Journal Information:

Journal Volume: 8; Journal Issue: 4; Journal ID: ISSN 2451-9294

Publisher:

Cell Press

Country of Publication:

United States

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; perovskites; GIWAXS; mechanism; kinetics