TY - JOUR
T1 - Carrier Localization on the Nanometer-Scale limits Transport in Metal Oxide Photoabsorbers
AU - Schleuning, Markus
AU - Kölbach, Moritz
AU - Ahmet, Ibbi
AU - Präg, Raphael
AU - Gottesman, Ronen
AU - Gunder, René
AU - Zhang, Mengyuan
AU - Wargulski, Dan Ralf
AU - Abou-Ras, Daniel
AU - Grave, Daniel A.
AU - Abdi, Fatwa F.
AU - van de Krol, Roel
AU - Schwarzburg, Klaus
AU - Eichberger, Rainer
AU - Friedrich, Dennis
AU - Hempel, Hannes
PY - 2023/6/19
Y1 - 2023/6/19
N2 - Metal oxides are considered as stable and low-cost photoelectrode candidates for hydrogen production by photoelectrochemical solar water splitting. However, their power conversion efficiencies usually suffer from poor transport of photogenerated charge carriers, which has been attributed previously to a variety of effects occurring on different time and length scales. In search for common understanding and for a better photo-conducting metal oxide photoabsorber, CuFeO2, α-SnWO4, BaSnO3, FeVO4, CuBi2O4, α-Fe2O3, and BiVO4 are compared. Their kinetics of thermalization, trapping, localization, and recombination are monitored continuously 100 fs–100 µs and mobilities are determined for different probing lengths by combined time-resolved terahertz and microwave spectroscopy. As common issue, we find small mobilities < 3 cm2V-1s-1. Partial carrier localization further slows carrier diffusion beyond localization lengths of 1–6 nm and explains the extraordinarily long conductivity tails, which should not be taken as a sign of long diffusion lengths. For CuFeO2, the localization is attributed to electrostatic barriers that enclose the crystallographic domains. The most promising novel material is BaSnO3, which exhibits the highest mobility after reducing carrier localization by annealing in H2. Such overcoming of carrier localization should be an objective of future efforts to enhance charge transport in metal oxides. © 2023 The Authors. Advanced Functional Materials published by Wiley-VCH GmbH.
AB - Metal oxides are considered as stable and low-cost photoelectrode candidates for hydrogen production by photoelectrochemical solar water splitting. However, their power conversion efficiencies usually suffer from poor transport of photogenerated charge carriers, which has been attributed previously to a variety of effects occurring on different time and length scales. In search for common understanding and for a better photo-conducting metal oxide photoabsorber, CuFeO2, α-SnWO4, BaSnO3, FeVO4, CuBi2O4, α-Fe2O3, and BiVO4 are compared. Their kinetics of thermalization, trapping, localization, and recombination are monitored continuously 100 fs–100 µs and mobilities are determined for different probing lengths by combined time-resolved terahertz and microwave spectroscopy. As common issue, we find small mobilities < 3 cm2V-1s-1. Partial carrier localization further slows carrier diffusion beyond localization lengths of 1–6 nm and explains the extraordinarily long conductivity tails, which should not be taken as a sign of long diffusion lengths. For CuFeO2, the localization is attributed to electrostatic barriers that enclose the crystallographic domains. The most promising novel material is BaSnO3, which exhibits the highest mobility after reducing carrier localization by annealing in H2. Such overcoming of carrier localization should be an objective of future efforts to enhance charge transport in metal oxides. © 2023 The Authors. Advanced Functional Materials published by Wiley-VCH GmbH.
KW - carrier localization
KW - metal oxides
KW - mobilities
KW - photoconductivity
KW - water splitting
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U2 - 10.1002/adfm.202300065
DO - 10.1002/adfm.202300065
M3 - RGC 21 - Publication in refereed journal
SN - 1616-301X
VL - 33
JO - Advanced Functional Materials
JF - Advanced Functional Materials
IS - 25
M1 - 2300065
ER -