Phase transformation from solvate phase to perovskite: Phase diagram of a mixed halide system Anton Dzhong 1,2 , Maxim Simmonds 2 , Feray Ünlü 2 , Dominik Al-Sabbagh 3 , Franziska Emmerling 3 , Eva Unger 1,2 1 HU Berlin, Department of Chemistry,Berlin, Germany 2 Solar Energy Division, Berlin, Germany 3 Bundesanstalt für Materialforschung und -prüfung, Berlin, Germany When fabricating perovskite solar cells (PSCs) several deposition and formation pathways of the absorber layer can be used, while all of them inherit a crystallisation of the perovskite. The focus of this work is lying on a precursor of the crystallisation: perovskite solvate phases (PSPs). PSPs have mostly been viewed as a troubling intermediate, which should be of smallest impact as possible for the synthesis of homogeneous perovskite thin films. However, our hypothesis is that as a pre-structure of the resulting perovskite, the PSP might be a necessary intermediate to influence certain characteristics (e.g., defect proclivity, halide homogeneity) of the crystallisation product. As first approach we decipher the role of the antisolvent in the crystallisation, with different solvent|antisolvent systems being used for the precursor synthesis. Structural analysis of the differently synthesised PSPs identifies differences in microscopic functionality between the used antisolvents and analogous structural differences in the resulting lattices. To then study the material nature of perovskite crystallisation from PSPs, MA 2 (DMF) 2 Pb2(Br x I 1-x ) 6 -PSP crystals are investigated while heating (to simulate thermal annealing for thin films). The induced phase transformation to perovskite is monitored mainly via X-ray diffractometry showing the structural evolution of the lattice, while thermo-gravimetric analysis confirms the chemical decomposition of the PSP. The result of this work will be a phase diagram of MAPb(Br x I 1-x ) 3 in presence of a solvent showing temperature dependant phase boundaries in the halide spectrum from iodide to bromide. Exhibiting basic information about perovskite crystallisation this approach might be of use for a broad community, being applicable in PSC fabrication. References 1. C. Rehermann, A. Merdasa, K. Suchan, V. Schröder, F. Mathies, E. L. Unger, ACS Appl.Mater. Interfaces 2020, 12, 30343– 30352 2. W. Mao, J. Zheng, Y. Zhang, A. S. R. Chesman, Q. Ou, J. Hicks, F. Li, Z. Wang, B.Graystone, T. D. M. Bell, M. U. Rothmann, N. W. Duffy, L. Spiccia, Y. Cheng, Q. Bao, U. Bach, Angew. Chem. 2017, 129, 12660–12665 3. S. A. Fateev, A. A. Petrov, V. N. Khrustalev, P. V. Dorovatovskii, Y. V. Zubavichus, E. A.Goodilin, A. B. Tarasov, Chem. Mater. 2018, 30, 5237–5244 4. F. Hao, C. C. Stoumpos, Z. Liu, R. P. H. Chang, M. G. Kanatzidis, J. Am. Chem. Soc.2014, 136, 16411–16419 5. A. A. Petrov, I. P. Sokolova, N. A. Belich, G. S. Peters, P. V. Dorovatovskii, Y. V.Zubavichus, V. N. Khrustalev, A. V. Petrov, M. Grätzel, E. A. Goodilin, A. B. Tarasov, J. Phys. Chem. C 2017, 121, 20739–20743 6. K. Suchan, J. Just, P. Beblo, C. Rehermann, A. Merdasa, R. Mainz, I. G. Scheblykin, E.Unger, Advanced Functional Materials 2023, 33, 2206047 7. J. Cao, X. Jing, J. Yan, C. Hu, R. Chen, J. Yin, J. Li, N. Zheng, J. Am. Chem. Soc. 2016,138, 9919–9926
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