On the relation between the open-circuit voltage and quasi-fermi level splitting in efficient perovskite solar cells
- Today's perovskite solar cells (PSCs) are limited mainly by their open‐circuit voltage (VOC) due to nonradiative recombination. Therefore, a comprehensive understanding of the relevant recombination pathways is needed. Here, intensity‐dependent measurements of the quasi‐Fermi level splitting (QFLS) and of the VOC on the very same devices, including pin‐type PSCs with efficiencies above 20%, are performed. It is found that the QFLS in the perovskite lies significantly below its radiative limit for all intensities but also that the VOC is generally lower than the QFLS, violating one main assumption of the Shockley‐Queisser theory. This has far‐reaching implications for the applicability of some well‐established techniques, which use the VOC as a measure of the carrier densities in the absorber. By performing drift‐diffusion simulations, the intensity dependence of the QFLS, the QFLS‐VOC offset and the ideality factor are consistently explained by trap‐assisted recombination and energetic misalignment at the interfaces. Additionally, itToday's perovskite solar cells (PSCs) are limited mainly by their open‐circuit voltage (VOC) due to nonradiative recombination. Therefore, a comprehensive understanding of the relevant recombination pathways is needed. Here, intensity‐dependent measurements of the quasi‐Fermi level splitting (QFLS) and of the VOC on the very same devices, including pin‐type PSCs with efficiencies above 20%, are performed. It is found that the QFLS in the perovskite lies significantly below its radiative limit for all intensities but also that the VOC is generally lower than the QFLS, violating one main assumption of the Shockley‐Queisser theory. This has far‐reaching implications for the applicability of some well‐established techniques, which use the VOC as a measure of the carrier densities in the absorber. By performing drift‐diffusion simulations, the intensity dependence of the QFLS, the QFLS‐VOC offset and the ideality factor are consistently explained by trap‐assisted recombination and energetic misalignment at the interfaces. Additionally, it is found that the saturation of the VOC at high intensities is caused by insufficient contact selectivity while heating effects are of minor importance. It is concluded that the analysis of the VOC does not provide reliable conclusions of the recombination pathways and that the knowledge of the QFLS‐VOC relation is of great importance.…
Author details: | Pietro CaprioglioORCiDGND, Martin StolterfohtORCiDGND, Christian Michael WolffORCiDGND, Thomas UnoldORCiD, Bernd Rech, Steve Albrecht, Dieter NeherORCiDGND |
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DOI: | https://doi.org/10.1002/aenm.201901631 |
ISSN: | 1614-6832 |
ISSN: | 1614-6840 |
Title of parent work (English): | advanced energy materials |
Publisher: | Wiley-VCH |
Place of publishing: | Weinheim |
Publication type: | Article |
Language: | English |
Date of first publication: | 2019/07/25 |
Publication year: | 2019 |
Release date: | 2021/02/04 |
Tag: | electro-optical materials; perovskite solar cells; photovoltaic devices; thin films |
Volume: | 9 |
Issue: | 33 |
Number of pages: | 10 |
Funding institution: | German Federal Ministry of Education and Research (BMBF), within the project "Materialforschung fur die Energiewende"Federal Ministry of Education & Research (BMBF) [03SF0540]; German Federal Ministry for Economic Affairs and Energy (BMWi) through the "PersiST" project [0324037C]; HyPerCells (a Joint Graduate School of the Potsdam University); HyPerCells (HZB); Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)German Research Foundation (DFG) [182087777, SFB 951] |
Organizational units: | Mathematisch-Naturwissenschaftliche Fakultät / Institut für Physik und Astronomie |
DDC classification: | 6 Technik, Medizin, angewandte Wissenschaften / 60 Technik / 600 Technik, Technologie |
Peer review: | Referiert |
Publishing method: | Open Access / Hybrid Open-Access |
License (German): | CC-BY - Namensnennung 4.0 International |
External remark: | Zweitveröffentlichung in der Schriftenreihe Postprints der Universität Potsdam :[Mathematisch-Naturwissenschaftliche Reihe]; [774] |