Journal
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
Volume 11, Issue 19, Pages 8417-8423Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.jpclett.0c02331
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Funding
- European Union's Horizon 2020 MSCA Innovative Training Network [764787]
- Ministerio de Economia y Competitividad (MINECO) from Spain [ENE2017-85087-C3-1-R]
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Negative capacitance in the low-frequency domain and inverted hysteresis are familiar features in perovskite solar cells, which origin is still under discussion. Here we use impedance spectroscopy to analyze these responses in methylammonium lead bromide cells treated with lithium cations at the electron-selective layer/perovskite interface and in iodide devices exposed to different relative humidity conditions. Employing the surface polarization model, we obtain a time constant associated with the kinetics of the interaction of ions/vacancies with the surface, tau(kin), in the range of 10(0)-10(2) s for all the cases exhibiting both features. These interactions lead to a decrease in the overall recombination resistance, modifying the low-frequency perovskite response and yielding a flattening of the cyclic voltammetry. As a consequence of these results we find that negative capacitance and inverted hysteresis lead to a decrease in the fill factor and photovoltage values.
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