Dr. Davide Moia

Our team’s research concerns the defect chemistry of hybrid halide perovskites. These compounds show exceptional performance when used as active materials for solar cells, however they suffer from long time variations in their optoelectronic behavior. Previous research from our department revealed significant ion conduction in methylammonium lead iodide (MAPI), which is the archetype composition in this family of materials.1 The transport of ions underlies many of the anomalous features observed in hybrid perovskite devices. Iodide vacancies are the majority carriers and the “ionic protagonists” influencing the electrical behavior of MAPI.2

Fig. 1. Measurements of hybrid perovskite devices under controlled component partial pressure, light exposure and electrical bias are used to connect the device physics of these devices with the active material’s defect chemistry.

Our work focuses on the characterization of mixed conduction in hybrid perovskites using established techniques in the field of solid state ionics and extending them to the out of equilibrium conditions, relevant to photovoltaic applications (see Fig. 1).

Our current efforts are aimed to clarify the process of ion migration and its impact on several aspects related to the behavior of MAPI and other hybrid perovskites:

  • Analysis of electrochemical impedance spectroscopy of hybrid perovskite devices
  • Ion transport and photo-induced phase instability in mixed halide perovskites (PhD student Ya-Ru Wang)
  • Nanoionics of hybrid perovskite interfaces (PhD student Mina Jung)
  • Ionics of 2D layered perovskites (PhD student Algirdas Dučinskas, collaboration with Prof. Grätzel at EPFL)
  • Optoionics of hybrid perovskites

1. Yang, T. Y., Gregori, G., Pellet, N., Grätzel, M. & Maier, J. The Significance of Ion Conduction in a Hybrid Organic-Inorganic Lead-Iodide-Based Perovskite Photosensitizer. Angew. Chemie - Int. Ed. 54, 7905–7910 (2015).

2. Senocrate, A. et al. The Nature of Ion Conduction in Methylammonium Lead Iodide: A Multimethod Approach. Angew. Chemie Int. Ed. 56, 7755–7759 (2017).

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