Observation of Surface Polarization at Hybrid Perovskite/Au Interfaces by Transient Experiments
Marisé García-Batlle a, Jorge Caram a b c, Osbel Almora a d e, Roberto D. Arce b c, Antonio Guerrero a, Germà Garcia-Belmonte a
a Universitat Jaume I, Institute of Advanced Materials (INAM) - Spain, Avinguda de Vicent Sos Baynat, Castelló de la Plana, Spain
b Instituto de Física del Litoral (IFIS-CONICET), Argentina, Güemes, 3450, Santa Fe, Argentina
c Facultad de Ingeniería Química, Universidad Nacional del Litoral, Sgo. Del Estero 2829, S3000
d Institute of Materials for Electronics and Energy Technology (i-MEET), Friedrich-Alexander Universität Erlangen-Nürnberg,Germany, Martensstraße, 7, Erlangen, Germany
e Erlangen Graduate School in Advanced Optical Technologies (SAOT), Friedrich-Alexander Universität Erlangen-Nürnberg, Germany, Paul-Gordan-Straße, 6, Erlangen, Germany
nanoGe Perovskite Conferences
Proceedings of International Conference on Perovskite Thin Film Photovoltaics and Perovskite Photonics and Optoelectronics (NIPHO20)
Sevilla, Spain, 2020 February 23rd - 25th
Organizer: Hernán Míguez
Poster, Marisé García-Batlle, 101
Publication date: 25th November 2019

Hybrid perovskite light-absorbing materials own a distinctive feature, the non-negligible ionic conductivity that is believed to influence photovoltaic operation. Moving ions or vacancies can naturally accumulate at the outer interfaces (electrode polarization) upon biasing. Then, a modulation of conductive or recombination properties could manifest as an alteration in the low-frequency part of the impedance response, either producing inductive or large capacitive features. It is still under debate whether large capacitive effects observed at low-frequencies in PSCs are exclusively explained from charge accumulation mechanisms (interface polarization) or a dynamic interplay between ionic kinetics and electronic carrier recombination/injection current is occurring giving rise to apparent (not real) capacitors. Our work intends to provide new evidences that assist us in distinguishing between real charge polarization and delayed current effects under bias stimuli in the dark. The analysis relays upon an experimental technique based on transient charging signals using the Sawyer-Tower circuit. Our findings reveal that real steady-state charge is induced by the applied voltage in the dark, easily interpreted by means of charged real capacitors with values much larger than the film geometrical capacitance. The connection between that polarization and the charging of perovskite/contact interfaces is highlighted.

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