Key question which will be answered in the scope of the project.  Realization of objectives, tackled in synergy by both experimental techniques and theoretical approaches, will enhance our understanding of the relationships between the unique physical properties of 2D perovskites such as excitonic properties and electron–phonon (e-ph) coupling, and of organic spacer engineering, quantum well thickness, formation energies of phases with different n, crystal orientation, transport dynamics and resulting optoelectronic performance. Theoretical and computational exploration will provide improved understanding on the relation between structure, namely dimensionality, and the resulting properties, hence allowing to rationalize elements for better device performances. We will simultaneously focus on the organic-spacer frame, in term of its structural features, and on the inorganic scaffold, to determine if the deformation and presence of defects affect the optical and electronic properties. The consequences of their pairing will be also strongly investigated. We aim to quantitatively address elements able to guide synthesis and development of new strategies for future perovskite-based optoelectronic devices. Systematic study carried out in such an ample manner should provide an insight to complex interplay between the choice of perovskite building blocks and formation of perovskites with low defect concentrations, finally leading to the improved device stability and efficiency.

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Specific objectives.

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O1. Preparation, characterization and theoretical calculations of the Ruddlesden-Popper series:

A2A’n-1PbnX3n+1 (n=1-4; A=n-BA, i-BA, t-BA; PA, PNA, HA; NA, BZA, PEA, PPA; A’=MA; X=Br or I)

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O2. Establishing a two-way communication: Elucidation of the relationship between the choice of spacer ammonium cation A and the formation, structure and properties of RP perovskites by experimental techniques and rationalization of experimental findings by the theoretical calculations.

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O3. Quest for the best: selection of best RP material according to on both experimental results and theoretical arguments. Optimization of thin film deposition, device assembly and characterization.

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O4. Towards the rational synthesis in O5: Selection of best candidates via computational screening of Dion-Jacobson series: AA’n-1PbnX3n+1 (n=1-4; A=2-EDA, 1,8-ODA, 1,4-DE-1,8-ODA, BPDA, 2,6-NDA, 1,4-PDMA and 1,4-PDEA; A’=MA; X= Br or I) by the classical and ab initio molecular dynamics and DFT.

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O5. Preparation and characterization and theoretical calculations of Dion-Jacobson series: 

AA’n-1PbnX3n+1 (n=1-4; A=1,4-BDA, 2,3-BDA, 1,6-HDA; A’=MA; X= Br or I) and plus best identified cations as predicted by theory.

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O6. Establishing a two-way communication: Elucidation of the relationship between the choice of space diammonium cation A and the formation, structure and properties of DJ perovskites by experimental techniques and rationalization of experimental findings by the theory calculations.

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O7. Quest for the best: selection of best DJ material according to both experimental results and theoretical arguments. Optimization of thin film deposition, device assembly and characterization.

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O8. Building up and deepening the knowledge about 2D and quasi-2D halide perovskites in order to identify further research directions.

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Key words. Halide perovskites, Ruddlesden-Popper, Dion-Jacobson, photoluminescence, crystal structure, theoretical calculations, DFT, LED and solar cell applications