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π‐Conjugated Organic–Inorganic Hybrid Photoanodes: Revealing the Photochemical Behavior through In Situ X‐Ray Absorption Spectroscopy
Author(s) -
Hsu ChiaShuo,
Węcławski Marek K.,
Koszarna Beata,
Gryko Daniel T.,
Chen Hao Ming
Publication year - 2018
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201804829
Subject(s) - homo/lumo , photochemistry , xanes , absorption (acoustics) , absorption spectroscopy , semiconductor , spectroscopy , organic semiconductor , materials science , molecule , charge carrier , conjugated system , chemistry , optoelectronics , polymer , organic chemistry , optics , physics , quantum mechanics , composite material
Small‐molecule organic semiconductors exhibit great potential for the photoelectrochemical oxidation of water because of their n‐type semiconductor nature and their tunable bandgaps. In this work, several head‐to‐tail bis‐coumarins were synthesized and their photophysical properties characterized. Their characteristics as n‐type semiconductors were modified by varying the electronic character of substituents at positions 1 and 7, which enabled the energy level of the LUMO and the photoinduced charge‐carrier‐transfer efficiency to be modulated. X‐Ray absorption near‐edge structure (XANES) spectroscopy confirmed that the charge transfer is a crucial factor contributing to the resulting activity of the photoanode. The photoactivity of the photoanodes towards water oxidation was revealed to be governed by both the LUMO energy level and transfer efficiency of the photoinduced charge carriers. Among the studied molecules, a bis‐coumarin with benzothiophenyl substituents showed the greatest potential as light absorber for photoelectrochemical water oxidation.