Measurement and Interpretation of Mixed Ionic-Electronic Conductivity in Halide Perovskite Devices
Davide Moia a, Mina Jung a, Ya-Ru Wang a, Joachim Maier a
a Max Planck Institute for Solid State Research, Heisenbergstraße, 1, Stuttgart, Germany
Proceedings of Device Physics Characterization and Interpretation in Perovskite and Organic Materials (DEPERO)
València, Spain, 2023 October 3rd - 5th
Organizers: Sandheep Ravishankar, Juan Bisquert and Evelyne Knapp
Oral, Davide Moia, presentation 022
Publication date: 14th September 2023

Understanding the role of mobile ionic defects in hybrid perovskite devices is one of the most important challenges in the field of perovskite optoelectronics. Progress in this direction relies on the development of appropriate experimental methods able to probe mixed conduction in these materials, and of models that can provide an accessible, yet accurate, interpretation of device function. [1]

In this contribution, we highlight important aspects in the charge carrier chemistry of mixed conducting halide perovskites at equilibrium. First, we present a systematic approach to the investigation of mixed conduction in methylammonium lead iodide (MAPI) thin films based on horizontal device structures. The results highlight the importance of electrode charging in the long time scale polarization behavior of MAPI devices, [2] consistent with the dynamics of electric field screening in MAPI devices probed with spectroscopic and optoelectronic methods. [3] Further ionic interactions occurring at interfaces at equilibrium are presented, emphasizing the role of mobile ionic defects in the determination of space charge equilibrium in mixed conducting solar cells. [4] To facilitate the discussion of these aspects, we refer to generalized energy diagrams, where the representation of both the ionic and the electronic properties are combined. [5,6] This also highlights the importance of the halogen partial pressure, as a knob for the control of stoichiometry and, therefore of mixed conductivity. We conclude by giving a perspective on how the understanding of the material’s behavior at equilibrium can be extended to the situation under light and voltage bias.

We thank Achim Gueth, Marion Hagel and Ulrike Waizmann (Nanostructuring Lab in the Max Planck Institute for Solid State
Research, Juergen Weis’ group), Dr Helga Hoier, Florian Kaiser, Dr Rotraut Merkle (Physical Chemistry of Solids Department). DM is grateful to the Alexander von Humboldt Foundation for financial support.

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