Octahedral tilt engineering: atomic-level picture of stabilized α-FAPbI3

DOI: 10.29363/nanoge.hpatom.2022.000

Authors: Tiarnan A. S. Doherty (University of Cambridge) , Dominik Kubicki (University of Cambridge) , Stuart Macpherson (University of Cambridge) , Young-Kwang Jung (Yonsei University) , Duncan Johnstone (University of Cambridge) , Affan Iqbal (University of Cambridge) , Dengyang Guo (University of Cambridge) , Kyle Frohna (University of Cambridge) , Mohsen Danaie (Diamond Light Source; University of Oxford) , Elizabeth Tennyson (University of Cambridge) , Satyawan Nagane (University of Cambridge) , Anna Abfalterer (University of Cambridge) , Miguel Anaya (University of Cambridge) , Yu-Hsien Chiang (University of Cambridge) , Phillip Crout (University of Cambridge) , Francesco Simone Ruggeri (Wageningen University and Research) , Sean Collins (University of Leeds) , Clare Grey (University of Cambridge) , Aron Walsh (Yonsei University; Imperial College London) , Paul Midgley (University of Cambridge) , Samuel Stranks (University of Cambridge)
Co-authored by industrial partner: No

Type: Conference Paper
Conference: Online Conference on Atomic-level Characterisation of Hybrid Perovskites (HPATOM2)
Peer Reviewed: No

State: Published (Approved)
Published: February 2022
Diamond Proposal Number(s): 20420 , 24111

Abstract: There is currently substantial interest in stabilizing the simple ternary FAPbI3 perovskite because of its near-optimal band gap and superior thermal stability compared to methylammonium-based materials.1 The key challenge of FAPbI3 is the thermodynamic instability of the polymorph required for efficient light harvesting. Without additives, the black photoactive α-polymorph is only stable above ca. 160°C. At room temperature, it is metastable and rapidly transitions to the non-perovskite yellow polymorph. The stabilization of the black polymorph at room temperature can be achieved, for example, by adding a small amount of the pernicious MA through use of methylammonium chloride (in conjunction with formamidinium formate),2 methylammonium thiocyanate,3 or methylammonium formate.4 We have developed a new stabilization strategy which does not involve the addition of MA.5 Instead, it uses a surface-templating agent (EDTA) which modifies the material without incorporating into the structure. We use a combination of scanning electron diffraction (SED) and nuclear magnetic resonance spectroscopies (NMR, NQR) to identify the atomic-level mechanism of action of EDTA in this role. We find that it templates the structure by inducing a small octahedral tilt, only resolvable with local characterization techniques, and imparts remarkable phase stability by arresting transitions to low-dimensional polymorphs. This octahedral tilt engineering strategy is remarkably universal, and we show that it is the intrinsic stabilization mechanism in the state-of-the-art FA-rich mixed-cation materials.

Diamond Keywords: Photovoltaics; Semiconductors

Subject Areas: Materials, Chemistry, Energy

Diamond Offline Facilities: Electron Physical Sciences Imaging Centre (ePSIC)
Instruments: E02-JEM ARM 300CF , I14-Hard X-ray Nanoprobe

Added On: 15/02/2022 09:34

Discipline Tags:

Earth Sciences & Environment Sustainable Energy Systems Energy Climate Change Physical Chemistry Energy Materials Chemistry Materials Science Perovskites Metallurgy

Technical Tags:

Diffraction Microscopy Electron Microscopy (EM) Scanning Electron Microscopy (SEM)