Photo De-Mixing in Mixed Bromide-Iodide Perovskites: Dimensionality and Encapsulation Effects on Ionic & Electronic Transport Properties

Ya-Ru Wang^a, Marko Mladenović^b, Rothlisberger Ursula^b, Milić Jovana V.^c, Moia Davide^a, Grätzel Michael^d, Maier Joachim^a

^aMax Planck Institute for Solid State Research, Stuttgart, Germany.

^bLaboratory of Computational Chemistry and Biochemistry, Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.

^cAdolphe Merkle Institute, University of Fribourg, Fribourg, 1700, Switzerland

^dLaboratory of Photonics and Interfaces, Ecole polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.

International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV24)

València, Spain, 2024 May 12th - 15th

Organizer: Bruno Ehrler

Oral, Ya-Ru Wang, presentation 084
Publication date: 6th February 2024

Mixtures of bromide and iodide in halide perovskites provide solutions for tunable optoelectronic material design. However, such mixtures suffer from photo-induced phase segregation when exposed to light (photo de-mixing)^[1]. While the process is reversible (two phases remix back in the dark to the pristine state, dark re-mixing),^[2] it can potentially lead to unstable optoelectronic properties and device performance during operation, making its understanding essential to progress the field of halide perovskites. Since the observed light-induced phase separation involves significant ion transport, clarifying the ionic and electronic transport properties and therefore underlying defect chemical mechanisms involved in photo de-mixing is crucial.

Here, mixed bromide-iodide perovskites with different dimensionalities (2D, 3D) are investigated, in terms of phase and charge transport properties using a wide range of experimental techniques as well as theoretical calculations. We focus on 2D Dion-Jacobson mixed bromide-iodide perovskites (PDMA)Pb(Br_0.5I_0.5)₄ (PDMA: 1,4-phenylenedimethanammonium spacer) as a model system to study photo de-mixing, due to its established reversibility.^[2] Firstly, we track the compositional evolution in the films during de-mixing and re-mixing by analyzing their time-dependent in-situ optical absorption properties. We also simultaneously monitor the conductivity changes during de-mixing and re-mixing, which allows for a local probe of the ionic and electronic charge carriers concentration and ion transport through the de-mixed phases. The dependence of the phase behavior and charge transport properties of mixed halide perovskites by varying dimensionality and surface conditions is further revealed using similar techniques. Furthermore, we take advantage of SEM and TEM to investigate the morphological changes and the nature of the iodide-rich and bromide-rich phases resulting from phase segregation. Lastly, we propose a model that considers possible opto-ionic effects, which can contribute to the driving force of de-mixing^{[3, 4]} and should therefore be considered in the overall energy balance of the process, together with the electronic effects discussed in the literature.^[5]Our work sheds light on fundamental questions related to the phase behavior and the role of defects on the driving force of de-mixing. These findings will also aid compositional engineering related to halide mixtures, which will enable the optimization of optoelectronic devices as well as the development of other emerging systems exploiting photo de-mixing or in general photo-ionic effects.

References:

[1] Hoke E.T.;Slotcavage D.J.;Dohner E.R.;Bowring A.R.;Karunadasa H.I., McGehee M.D. Reversible photo-induced trap formation in mixed-halide hybrid perovskites for photovoltaics. Chem Sci. 2015;6(1):613-617.

[2] Wang Y.-R.;Senocrate A.;Mladenović M.;Dučinskas A.;Kim G.Y.;Rothlisberger U., et al. Photo De-Mixing in Dion-Jacobson 2D Mixed Halide Perovskites. Adv Energy Mater. 2022;12(26):2200768

[3] Kim G.Y.;Senocrate A.;Wang Y.-R.;Moia D., Maier J. Photo-Effect on Ion Transport in Mixed Cation and Halide Perovskites and Implications for Photo-Demixing**. Angew Chem Int Ed. 2021;60(2):820-826.

[4] Wang Y.-R.;Kim G.Y.;Kotomin E.;Moia D., Maier J. Photo de-mixing in mixed halide perovskites: the roles of ions and electrons. JPhys Energy. 2022;4(1):011001.

[5] Draguta S.;Sharia O.;Yoon S.J.;Brennan M.C.;Morozov Y.V.;Manser J.S., et al. Rationalizing the light-induced phase separation of mixed halide organic-inorganic perovskites. Nat Commun. 2017;8(1):200. Acknowledgments:

Acknowledgements:

We thank the technical support from Nanostructuring Lab (NSL) and The Stuttgart Center for Electron Microscopy (StEM) in Max Planck Institute for Solid State Research. We are grateful to Helga Hoier, Armin Sorg for XRD measurements, Florian Kaiser, Udo Klock and Dr. Rotraut Merkle for technical assistance. DM is grateful to the Alexander von Humboldt Foundation for funding. This work was performed within the framework of the Max Planck-EPFL Center for Molecular Nano-science and Technology.

nanoGe is a prestigious brand of successful science conferences that are developed along the year in different areas of the world since 2009. Our worldwide conferences cover cutting-edge materials topics like perovskite solar cells, photovoltaics, optoelectronics, solar fuel conversion, surface science, catalysis and two-dimensional materials, among many others.

MATSUS

Previously nanoGe Spring Meeting (NSM) and nanoGe Fall Meeting (NFM), MATSUS is a multiple symposia conference focused on a broad set of topics of advanced materials preparation, their fundamental properties, and their applications, in fields such as renewable energy, photovoltaics, lighting, semiconductor quantum dots, 2-D materials synthesis, charge carriers dynamics, microscopy and spectroscopy semiconductors fundamentals, etc.

International Conference on Hybrid and Organic Photovoltaics

International Conference on Hybrid and Organic Photovoltaics (HOPV) is celebrated yearly in May. The main topics are the development, function and modeling of materials and devices for hybrid and organic solar cells. The field is now dominated by perovskite solar cells but also other hybrid technologies, as organic solar cells, quantum dot solar cells, and dye-sensitized solar cells and their integration into devices for photoelectrochemical solar fuel production.

Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics

The main topics of the Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics (IPEROP) are discussed every year in Asia-Pacific for gathering the recent advances in the fields of material preparation, modeling and fabrication of perovskite and hybrid and organic materials. Photovoltaic devices are analyzed from fundamental physics and materials properties to a broad set of applications. The conference also covers the developments of perovskite optoelectronics, including light-emitting diodes, lasers, optical devices, nanophotonics, nonlinear optical properties, colloidal nanostructures, photophysics and light-matter coupling.

International Conference on Perovskite Thin Film Photovoltaics Perovskite Photonics and Optoelectronics

The International Conference on Perovskite Thin Film Photovoltaics Perovskite Photonics and Optoelectronics (NIPHO) is the best place to hear the latest developments in perovskite solar cells as well as on recent advances in the fields of perovskite light-emitting diodes, lasers, optical devices, nanophotonics, nonlinear optical properties, colloidal nanostructures, photophysics and light-matter coupling.