The Device Physics of Metal Halide Perovskite Interfaces, Part 1: Drift-diffusion Simulations and Underlying Physics
Piers Barnes a, Davide Moia a, Ilario Gelmetti b c, Phil Calado a, William Fisher a, Michael Stringer d, Onkar Game d, Yinghong Hu e, Pablo Docampo e f, David Lidzey d, Emilio Palomares b g, Nelson Jenny a
a Department of Physics, Imperial College London, UK
b Institute of Chemical Research of Catalonia (ICIQ), Barcelona Institute of Science and Technology (BIST), Spain
c Departament d’Enginyeria Electrònica, Elèctrica i Automàtica, Universitat Rovira i Virgili, Avinguda dels Països Catalans, 26, Tarragona, Spain
d Department of Physics and Astronomy, University of Sheffield, UK
e Department of Chemistry and Center for NanoScience (CeNS), LMU München, Germany
f Physics Department, School of Electrical and Electronic Engineering, Newcastle University, UK
g ICREA – Institució Catalana de Recerça i Estudis Avançats, Passeig de Lluís Companys, 23, Barcelona, Spain
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV19)
Roma, Italy, 2019 May 12th - 15th
Organizers: Prashant Kamat, Filippo De Angelis and Aldo Di Carlo
Poster, Piers Barnes, 178
Publication date: 11th February 2019

We have recently introduced a circuit model for perovskite solar cells which encapsulates their key transient and frequency domain behaviour[1]. The circuit model was developed through analysis of our open source time-dependent drift-diffusion simulations which couple the effects of mobile ionic charge to the behaviour of free electrons and holes in the device (https://github.com/barnesgroupICL/Driftfusion). Not only do the simulations reproduce hysteresis in the current-voltage characteristics and transient behaviour of perovskite solar cells[2], they also reproduce impedance spectroscopy measurements[2]. We show that the apparently huge capacitances and inductances inferred from low-frequency impedance measurements arise from the out of phase modulation of recombination and injection across the interfaces and not from the accumulation and release of electronic charge at the interfaces. We will discuss the underlying assumptions and validity of the simulations, and the implied device physics. We show that the mechanism which relates mobile ionic charge redistribution (or surface polarisation) to the rate of interfacial electronic transfer is via an electrostatic ‘gating’ effect of the ions. This effect can be understood by drawing analogy with the charge transfer between the emitter and collector of a bipolar transistor where the current is modulated ‘gated’ by the potential applied to the transistor’s base.

[1] D. Moia, I. Gelmetti, P. Calado, W. Fisher, M. Stringer, O. Game, Y. Hu, P. Docampo, D. Lidzey, E. Palomares, J. Nelson, P. R. F. Barnes, Ionic-to-Electronic Current Amplification in Hybrid Perovskite Solar Cells. arXiv:1805.06446, 2018

[2] P. Calado, A. M. Telford, D. Bryant, X. Li, J. Nelson, B. C. O’Regan, P. R. F. Barnes, Evidence for Ion Migration in Hybrid Perovskite Solar Cells with Minimal Hysteresis. Nat. Commun. 2016, 7, 13831.

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