Ionic effects on space charge formation at selected interfaces of halide perovskites
MIna Jung a, Davide Moia a, Joachim Maier a
a Max Planck Institute for Solid State Research, Stuttgart, Germany, Germany
International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV23)
London, United Kingdom, 2023 June 12th - 14th
Organizers: Tracey Clarke, James Durrant and Trystan Watson
Poster, MIna Jung, 267
Publication date: 30th March 2023

The properties of interfaces between halide perovskites and charge transporting layers (CTL) are key to the charge carrier dynamics in solar cell devices. Processes including charge recombination and extraction largely determine the performance of the device and have been optimized through the development of interface passivation and modulation strategies [1-3]. The energy alignment and band bending at the interface between halide perovskite and adjacent layers is an important aspect in this context, but it is poorly understood. The space charge situation at the interface is commonly interpreted according to electronic equilibrium only. However, halide perovskites have mixed ionic-electronic conducting properties and the ionic interaction at their interfaces with contacting layer can have a critical impact on the determination of the space charge equilibrium [4]. Therefore, it is important to understand ion redistribution and ionically-generated space charge formation to design effective interfaces between halide perovskites and transporting layers.

In this study, we discuss experimental investigation of ionic effects in the space charge formation at selected interfaces of CH3NH3PbI3 (MAPI) where such effects are controlled. We focus our study on insulating and semiconducting oxides (e.g. Al2O3, TiO2) and we investigate the role of surface modification via sensitizing organic molecules. Zeta potential measurements are used to establish the expected ionic interaction between the oxides and MAPI. The ionic and electronic conductivities of MAPI are investigated as a function of the iodine partial pressure. The results allow us to extract the sign and magnitude of the space charge potential in MAPI when it is in contact with the oxides or with the organic molecules used for surface modification. We demonstrate that surface functionalization can modify the space charge situation at the interfaces with MAPI. Finally, we stress that a complete model describing the space charge situation at halide perovskite interfaces should include not only electronic equilibrium but also ionic effects. This study will help the design of perovskite devices with improved interfacial properties and the interpretation of experimental data accounting for the mixed conducting nature of halide perovskites.


[1] K. Hamada, R. Tanaka, MA. Kamarudin et al., ACS Appl. Mater. Interfaces 2020, 12, 17776−17782.

[2] J. Sun, C. Shou, J. Sun et al., Sol. RRL 2021, 5, 2100663

[3] M. Yang, X. Zhu, K. Mo et al., ACS Appl. Energy Mater. 2023

[4] GY. Kim, A. Senocrate, D. Moia, J. Maier, Adv. Funct. Mater. 2020, 30, 2002426.

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