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High Open Circuit Voltages in pin-Type Perovskite Solar Cells through Strontium Addition

Abstract

The incorporation of even small amounts of strontium (Sr) into lead-based quadruple cation hybrid perovskite solar cells results in a systematic increase of the open circuit voltage (Voc) in pin-type perovskite solar cells. We demonstrate via absolute and transient photoluminescence (PL) experiments how the incorporation of Sr significantly reduces the non-radiative recombination losses in the neat perovskite layer. We show that Sr segregates at the perovskite surface, where it induces important changes of morphology and energetics. Notably, the Sr-enriched surface exhibits a wider band gap and a more n-type character, accompanied with significantly stronger surface band bending. As a result, we observe a significant increase of the quasi-Fermi level splitting in the neat perovskite by reduced surface recombination and more importantly, a strong reduction of losses attributed to non-radiative recombination at the interface to the C60 electron-transporting layer. The resulting solar cells exhibited a Voc of 1.18 V, which could be further improved to nearly 1.23 V through addition of a thin polymer interlayer, bringing the non-radiative voltage loss to only 110 meV. Our work shows that simply adding a small amount of Sr to the precursor solutions induces a beneficial surface modification in the perovskite, without requiring any post treatment, resulting in high efficiency solar cells with power conversion efficiency (PCE) up to 20.3%. Our results demonstrate very high Voc values and efficiencies in Sr-containing quadruple cation perovskite pin solar cells and highlight the imperative importance of addressing and minimizing the recombination losses at the interface between perovskite and charge transporting layer.

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Publication details

The article was received on 19 Oct 2018, accepted on 07 Jan 2019 and first published on 09 Jan 2019


Article type: Paper
DOI: 10.1039/C8SE00509E
Citation: Sustainable Energy Fuels, 2019, Accepted Manuscript
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    High Open Circuit Voltages in pin-Type Perovskite Solar Cells through Strontium Addition

    P. Caprioglio, F. Zu, C. M. M. Wolff, J. A. Márquez Prieto, M. Stolterfoht, P. Becker, N. Koch, T. Unold, B. Rech, S. Albrecht and D. Neher, Sustainable Energy Fuels, 2019, Accepted Manuscript , DOI: 10.1039/C8SE00509E

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