Ions and Electrons in Halide Perovskites—Bulk vs Interfaces

The first part of the presentation summarizes parts of our work on bulk ion conductivity in halide perovskites. It deals with identifying the respective ionic and electronic charge carriers, discusses the adjusting screws for changing their concentrations as well as the relevance for polarization phenomena and stability. The surprising finding that light enhances the ion conductivity in the iodides [1] but not in the bromides, offers a simple explanation for the light induced demixing [2]. In the context of stability recent work on ion conduction in “hollow perovskites” [3] and “2D perovskites” [4] will be touched upon.<br/>The second part of the presentation refers to interfaces. It is shown that mobility of ions and the significant fraction of ionic charge carriers gives rise to ionically dominated built-in potentials, a point that had not been addressed in the photovoltaic literature and might lead to a paradigm change in the understanding of photoactive interfaces [4,5]. This ionic interaction “enslaves” the electronic redistribution, such that the electrons undergo a “fellow traveler effect”.<br/><br/>[1] G.Y. Kim et al., Nat. Mater. 17 (2018) 445<br/>[2] G.Y. Kim, A. Senocrate, Y. Wang, D. Moia, J. Maier, Angew. Chem. 60 (2021) 820; Y.-R. Wang et al., Adv. Energy Mater. 12 (2022) 2200768.<br/>[3] A. Senocrate et al., Chem. Mater. 33 (2021) 719.<br/>[4] A. Ducinskas et al., ACS Energy Letters 6 (2021) 337.<br/>[5] G.Y. Kim et al., Adv. Funct. Mater. 30 (2020) 2002426<br/>[6] D. Moia, J. Maier, ACS Energy Lett. 6 (2021) 1566