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Additive-Free, Low-Temperature Crystallization of Stable α-FAPbI3 Perovskite

Tian Du Orcid Logo, Thomas J. Macdonald Orcid Logo, Ruo Xi Yang Orcid Logo, Meng Li Orcid Logo, Zhongyao Jiang, Lokeshwari Mohan, Weidong Xu Orcid Logo, Zhenhuang Su, Xingyu Gao Orcid Logo, Richard Whiteley, Chieh‐Ting Lin Orcid Logo, Ganghong Min Orcid Logo, Saif A. Haque Orcid Logo, James Durrant Orcid Logo, Kristin A. Persson Orcid Logo, Martyn A. McLachlan, Joe Briscoe Orcid Logo

Advanced Materials, Volume: 34, Issue: 9, Start page: 2107850

Swansea University Author: James Durrant Orcid Logo

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DOI (Published version): 10.1002/adma.202107850

Abstract

Formamidinium lead triiodide (FAPbI3) is attractive for photovoltaic devices due to its optimal bandgap at around 1.45 eV and improved thermal stability compared with methylammonium‐based perovskites. Crystallization of phase‐pure α‐FAPbI3 conventionally requires high‐temperature thermal annealing a...

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Published in: Advanced Materials
ISSN: 0935-9648 1521-4095
Published: Wiley 2022
Online Access: Check full text

URI: https://cronfa.swan.ac.uk/Record/cronfa59285
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Abstract: Formamidinium lead triiodide (FAPbI3) is attractive for photovoltaic devices due to its optimal bandgap at around 1.45 eV and improved thermal stability compared with methylammonium‐based perovskites. Crystallization of phase‐pure α‐FAPbI3 conventionally requires high‐temperature thermal annealing at 150 °C whilst the obtained α‐FAPbI3 is metastable at room temperature. Here, aerosol‐assisted crystallization (AAC) is reported, which converts yellow δ‐FAPbI3 into black α‐FAPbI3 at only 100 °C using precursor solutions containing only lead iodide and formamidinium iodide with no chemical additives. The obtained α‐FAPbI3 exhibits remarkably enhanced stability compared to the 150 °C annealed counterparts, in combination with improvements in film crystallinity and photoluminescence yield. Using X‐ray diffraction, X‐ray scattering, and density functional theory simulation, it is identified that relaxation of residual tensile strains, achieved through the lower annealing temperature and post‐crystallization crystal growth during AAC, is the key factor that facilitates the formation of phase‐stable α‐FAPbI3. This overcomes the strain‐induced lattice expansion that is known to cause the metastability of α‐FAPbI3. Accordingly, pure FAPbI3 p–i–n solar cells are reported, facilitated by the low‐temperature (≤100 °C) AAC processing, which demonstrates increases of both power conversion efficiency and operational stability compared to devices fabricated using 150 °C annealed films.
Keywords: additive-free; aerosol-assisted crystallization; formamidinium lead triiodide; stability; strain
College: College of Engineering
Funders: EPSRC Plastic Electronics. Grant Number: EP/L016702/1; QMUL-EPSRC Impact Accelerator Account; Stephen and Anna Hui Scholarship; Imperial College London; U.S. Department of Energy; Office of Science; Basic Energy Sciences; Materials Sciences and Engineering Division. Grant Number: DE-AC02-05-CH11231; Global Research Laboratory; National Research Foundation of Korea. Grant Number: NRF-2017K1A1A2013153
Issue: 9
Start Page: 2107850