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  • 11
    Online Resource
    Online Resource
    Berlin : Humboldt-Universität zu Berlin
    UID:
    edochu_18452_28849
    Format: 1 Online-Ressource (8 Seiten)
    Content: We have witnessed tremendous progress of metal halide perovskite (MHP)-based optoelectronic devices, especially in the field of photovoltaics. Despite intensive research in the past few years, questions still remain regarding their fundamental optoelectronic properties, among which the electronic properties exhibit an interplay of numerous phenomena that deserve serious scrutiny. In this Focus article, we aim to provide a contemporary understanding of the unique electronic properties that has been resolved by the community. First introducing some of the basic concepts established in semiconductor physics, the intrinsic and extrinsic electronic properties of the MHPs are disentangled and explained. With this, the complex interplay of interface-, dopant-, and surface state-induced electronic states in determining the electrostatic landscape in the material can be comprehended, and the energy level alignment in device architectures more reliably assessed.
    Content: Peer Reviewed
    In: Cambridge : RSC Publ., 9,1, Seiten 17-24
    Language: English
    URL: Volltext  (kostenfrei)
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  • 12
    UID:
    edochu_18452_28916
    Format: 1 Online-Ressource (7 Seiten)
    Content: The electronic properties of metal halide perovskites (MHPs) are crucial for achieving the full potential of MHPs-based optoelectronic devices, and they are extensively studied by photoelectron spectroscopy (PES). However, there are numerous complexities during PES measurements, which can result in inconsistent experimental data or even misinterpretation of results. Here, it is demonstrated that in the presence of charge selective junctions with MHPs, significant electronic energy level realignment can occur during PES measurements due to the sample excitation with high-energy photons used in PES, amounting up to over 0.8 eV in the present case. This is caused by unbalanced charge carrier accumulation within the perovskite due to the charge-selective interface. X-ray photoelectron spectroscopy further reveals that photoexcitation due to bremsstrahlung, as produced in commonly employed twin-anode lab-sources, can readily produce sizable photoinduced shifts of core levels of MHPs films, whereas monochromatized X-ray lab-sources (irradiation flux reduced by 〉50 times by eliminating the bremsstrahlung) induce negligible shifts within the range of presently applied anode powers. The data and measurement conditions presented here are intended to enable others to obtain reliable MHP electronic property information from PES measurements.
    Content: Peer Reviewed
    Note: The article processing charge was funded by the Open Access Publication Fund of Humboldt-Universität zu Berlin.
    In: Weinheim : Wiley-VCH, 2023, 10,34
    Language: English
    URL: Volltext  (kostenfrei)
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  • 13
    UID:
    edochu_18452_29132
    Format: 1 Online-Ressource (6 Seiten)
    Content: One of the most promising routes for the future fabrication of solution-processable high-performance solar cells is to employ metal halide perovskites as photoactive material combined with organic semiconductors as charge extraction layers. An essential requirement to obtain high device performance is a proper energy level alignment across the device interfaces. Here, we investigate the interface between a triple cation perovskite and a prototypical electron acceptor molecule. Photoemission spectroscopy reveals a ground state charge transfer induced band bending on either side of the junction, which significantly alters the charge extraction barriers as compared to assumed vacuum level alignment and flat-band conditions. In addition, we demonstrate that upon white light illumination, the energy levels of the organic layer exhibit rigid shifts by up to 0.26 eV with respect to those of the perovskite, revealing a non-constant energy offset between the frontier energy levels of the two materials. Such level shifts of the organic transport layer are fully reversible upon switching on/off the light, indicating an electrostatic origin of this phenomenon caused by unbalanced distribution of photogenerated charge carriers. We therefore stress the importance of determining the energy level alignment at perovskite-based interfaces not only in the electronic ground state (dark) but also under device operating conditions (operando) to enable for a reliable correlation with the device performance.
    Content: Peer Reviewed
    In: New York : Springer, 129,4
    Language: English
    URL: Volltext  (kostenfrei)
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