Unraveling the Electronic Properties of Lead Halide Perovskites with Surface Photovoltage in Photoemission Studies
- The tremendous success of metal-halide perovskites, especially in the field of photovoltaics, has triggered a substantial number of studies in understanding their optoelectronic properties. However, consensus regarding the electronic properties of these perovskites is lacking due to a huge scatter in the reported key parameters, such as work function (Φ) and valence band maximum (VBM) values. Here, we demonstrate that the surface photovoltage (SPV) is a key phenomenon occurring at the perovskite surfaces that feature a non-negligible density of surface states, which is more the rule than an exception for most materials under study. With ultraviolet photoelectron spectroscopy (UPS) and Kelvin probe, we evidence that even minute UV photon fluxes (500 times lower than that used in typical UPS experiments) are sufficient to induce SPV and shift the perovskite Φ and VBM by several 100 meV compared to dark. By combining UV and visible light, we establish flat band conditions (i.e., compensate the surface-state-induced surface band bending)The tremendous success of metal-halide perovskites, especially in the field of photovoltaics, has triggered a substantial number of studies in understanding their optoelectronic properties. However, consensus regarding the electronic properties of these perovskites is lacking due to a huge scatter in the reported key parameters, such as work function (Φ) and valence band maximum (VBM) values. Here, we demonstrate that the surface photovoltage (SPV) is a key phenomenon occurring at the perovskite surfaces that feature a non-negligible density of surface states, which is more the rule than an exception for most materials under study. With ultraviolet photoelectron spectroscopy (UPS) and Kelvin probe, we evidence that even minute UV photon fluxes (500 times lower than that used in typical UPS experiments) are sufficient to induce SPV and shift the perovskite Φ and VBM by several 100 meV compared to dark. By combining UV and visible light, we establish flat band conditions (i.e., compensate the surface-state-induced surface band bending) at the surface of four important perovskites, and find that all are p-type in the bulk, despite a pronounced n-type surface character in the dark. The present findings highlight that SPV effects must be considered in all surface studies to fully understand perovskites’ photophysical properties.…
Author details: | Fengshuo Zu, Christian Michael WolffORCiDGND, Maryline Ralaiarisoa, Patrick AmsalemORCiD, Dieter NeherORCiDGND, Norbert KochORCiDGND |
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DOI: | https://doi.org/10.1021/acsami.9b05293 |
ISSN: | 1944-8244 |
ISSN: | 1944-8252 |
Pubmed ID: | https://pubmed.ncbi.nlm.nih.gov/31124647 |
Title of parent work (English): | ACS applied materials & interfaces |
Publisher: | American Chemical Society |
Place of publishing: | Washington |
Publication type: | Article |
Language: | English |
Date of first publication: | 2019/06/19 |
Publication year: | 2019 |
Release date: | 2021/01/20 |
Tag: | Kelvin probe; lead halide perovskite films; surface band bending; surface photovoltage; surface states; ultraviolet photoelectron spectroscopy |
Volume: | 11 |
Issue: | 24 |
Number of pages: | 6 |
First page: | 21578 |
Last Page: | 21583 |
Funding institution: | Helmholtz Energy Alliance "Hybrid Photovoltaics"; Joint Graduate School HyPerCells of the University of Potsdam; Joint Graduate School HyPerCells of the Helmholtz Zentrum Berlin; Potsdam Graduate School; DFGGerman Research Foundation (DFG) [SFB951, AM 419/1-1] |
Organizational units: | Mathematisch-Naturwissenschaftliche Fakultät / Institut für Physik und Astronomie |
DDC classification: | 5 Naturwissenschaften und Mathematik / 53 Physik / 530 Physik |
Peer review: | Referiert |