Nanoscale imaging of charge carrier transport in water splitting photoanodes

Eichhorn, Johanna; Kastl, Christoph; Cooper, Jason K.; Ziegler, Dominik; Schwartzberg, Adam; Sharp, Ian; Toma, Francesca M.

doi:10.1038/s41467-018-04856-8

Cited by 78 publications

(88 citation statements)

References 51 publications

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“…C‐AFM as a high‐sensitive characterization technique has been used to probe charge transport and electronic properties by measuring current under short‐circuit conditions . Generally, a large current under the same test condition indicates high conductivity of sample, which is beneficial to charge transport . On this basis, the conductivity discrepancy among different films can be studied and the transport behavior in grain interiors and at grain boundaries can be distinguished by C‐AFM with the nanoscale resolution.…”

Section: Applications Of C‐afm Techniquementioning

confidence: 99%

Emerging Conductive Atomic Force Microscopy for Metal Halide Perovskite Materials and Solar Cells

Zhang

et al. 2020

Advanced Energy Materials

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Metal halide perovskite materials, benefiting from a combination of outstanding optoelectronic properties and low‐cost solution‐preparation processes, show tremendous potential for optoelectronics and photovoltaics. However, the nanoscale inhomogeneities of the electronic properties of perovskite materials cause a number of difficulties, such as recombination, stability, and hysteresis, all of which seriously restrict device performance. Scanning probe microscopy, as a high‐resolution imaging technique, has been widely used to connect local properties and micro‐area morphologies to overall device performance. Conductive atomic force microscopy (C‐AFM) can realize a real‐space visualization of topography coupled with optoelectronic properties on a microscopic scale and thereby is uniquely suited to probe the local effects of perovskite materials and devices. The fundamental principles, alternative operation modes, and development of C‐AFM are comprehensively reviewed, and applications in perovskite solar cells (PSCs) for electronic transport behavior, ion migration and hysteresis, ferroelectric polarization, and facet orientation investigation are discussed. A comprehensive understanding and summary of up‐to‐date applications in PSCs is beneficial to further fully exploit the potential of such an emerging technique, so as to provide a novel and effective approach for perovskite materials analysis.

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Section: Applications Of C‐afm Techniquementioning

confidence: 99%

Emerging Conductive Atomic Force Microscopy for Metal Halide Perovskite Materials and Solar Cells

Zhang

et al. 2020

Advanced Energy Materials

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“…Although electrochemical measurements can macroscopically analyze the properties of photoanodes, the nanoscopic variations within the electrode or single particle are still not able to be determined by such ensemble experiments. We thus employed photoconductive atomic force microscopy (pc‐AFM) to elucidate structure‐correlated electrical transport properties inherent in individual MC particles with nanoscale resolution (Figure c–e; Supporting Information, Figure S11). Bias potentials ranging from −1.0 to 1.0 V were applied to the sample using a Ti/Ir‐coated conductive probe with a 25 nm tip radius, and the current was simultaneously collected under dark conditions or light irradiation in an N 2 atmosphere.…”

Section: Resultsmentioning

confidence: 99%

“…20 nm) showed a current onset (>0.25 V) in the low potential region (Figure e) due to Schottky contact. Schottky emission is an interface‐limited conduction that occurs at low voltages, whereby electrons transit above the potential barrier on the surface of a semiconductor . Both the Poole–Frenkel and Schottky emissions originate from lowering of the Coulombic potential barrier for free‐charge generation out of defect centers or trap sites under a bias potential .…”

Section: Resultsmentioning

confidence: 99%

Ultra‐Narrow Depletion Layers in a Hematite Mesocrystal‐Based Photoanode for Boosting Multihole Water Oxidation

2020

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Significant charge recombination that is difficult to suppress limits the practical applications of hematite (α‐Fe2O3) for photoelectrochemical water splitting. In this study, Ti‐modified hematite mesocrystal superstructures assembled from highly oriented tiny nanoparticle (NP) subunits with sizes of ca. 5 nm were developed to achieve the highest photocurrent density (4.3 mA cm−2 at 1.23 V vs. RHE) ever reported for hematite‐based photoanodes under back illumination. Owing to rich interfacial oxygen vacancies yielding an exceedingly high carrier density of 4.1×1021 cm−3 for super bulk conductivity in the electrode and a large proportion of ultra‐narrow depletion layers (<1 nm) inside the mesoporous film for significantly improved hole collection efficiency, a boosting of multihole water oxidation with very low activation energy (Ea=44 meV) was realized.

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“…The BiVO 4 thin films were illuminated from the FTO-side as in Ref. [16] . A CW-laser diode laser (405 nm) was used as light source.…”

Section: Methodsmentioning

confidence: 99%

Disentangling the Role of Surface Chemical Interactions on Interfacial Charge Transport at BiVO₄ Photoanodes

Eichhorn

Kastl

Schwartzberg

et al. 2018

ACS Appl. Mater. Interfaces

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Chemical transformations that occur on photoactive materials, such as photoelectrochemical water splitting, are strongly influenced by the surface properties as well as by the surrounding environment. Herein, we elucidate the effects of oxygen and water surface adsorption on band alignment, interfacial charge transfer, and charge-carrier transport by using complementary Kelvin probe measurements and photoconductive atomic force microscopy on bismuth vanadate. By observing variations in surface potential, we show that adsorbed oxygen acts as an electron-trap state at the surface of bismuth vanadate, whereas adsorbed water results in formation of a dipole layer without inducing interfacial charge transfer. The apparent change of trap state density under dry or humid nitrogen, as well as under oxygen-rich atmosphere, proves that surface adsorbates influence charge-carrier transport properties in the material. The finding that oxygen introduces electronically active states on the surface of bismuth vanadate may have important implications for understanding functional characteristics of water splitting photoanodes, devising strategies to passivate interfacial trap states, and elucidating important couplings between energetics and charge transport in reaction environments.

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Nanoscale imaging of charge carrier transport in water splitting photoanodes

Cited by 78 publications

References 51 publications

Emerging Conductive Atomic Force Microscopy for Metal Halide Perovskite Materials and Solar Cells

Emerging Conductive Atomic Force Microscopy for Metal Halide Perovskite Materials and Solar Cells

Ultra‐Narrow Depletion Layers in a Hematite Mesocrystal‐Based Photoanode for Boosting Multihole Water Oxidation

Disentangling the Role of Surface Chemical Interactions on Interfacial Charge Transport at BiVO₄ Photoanodes

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Nanoscale imaging of charge carrier transport in water splitting photoanodes

Cited by 78 publications

References 51 publications

Emerging Conductive Atomic Force Microscopy for Metal Halide Perovskite Materials and Solar Cells

Emerging Conductive Atomic Force Microscopy for Metal Halide Perovskite Materials and Solar Cells

Ultra‐Narrow Depletion Layers in a Hematite Mesocrystal‐Based Photoanode for Boosting Multihole Water Oxidation

Disentangling the Role of Surface Chemical Interactions on Interfacial Charge Transport at BiVO4 Photoanodes

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Disentangling the Role of Surface Chemical Interactions on Interfacial Charge Transport at BiVO₄ Photoanodes