Converting light energy to electrical energy in photovoltaic devices relies on the photogenerated electrons and holes separated by the built-in potential in semiconductors. Photo-excited electrons in metal electrodes are usually not considered in this process. Here, we report an enhanced photovoltaic effect in the ferroelectric lanthanum-modified lead zirconate titanate (PLZT) by using low work function metals as the electrodes. We believe that electrons in the metal with low work function could be photo-emitted into PLZT and form the dominant photocurrent in our devices. Under AM1.5 (100 mW/cm2) illumination, the short-circuit current and open-circuit voltage of Mg/PLZT/ITO are about 150 and 2 times of those of Pt/PLZT/ITO, respectively. The photovoltaic response of PLZT capacitor was expanded from ultraviolet to visible spectra, and it may have important impact on design and fabrication of high performance photovoltaic devices based on ferroelectric materials.
In this work, the excited-state hydrogen bonding dynamics of photoexcited coumarin 102 in aqueous solvent is reconsidered. The electronically excited states of the hydrogen bonded complexes formed by coumarin 102 (C102) chromophore and the hydrogen donating water solvent have been investigated using the time-dependent density functional theory method. Two intermolecular hydrogen bonds between C102 and water molecules are considered. The previous works (Wells et al., J Phys Chem A 2008, 112, 2511) have proposed that one intermolecular hydrogen bond would be strengthened and the other one would be cleaved upon photoexcitation to the electronically excited states. However, our theoretical calculations have demonstrated that both the two intermolecular hydrogen bonds between C102 solute and H(2)O solvent molecules are significantly strengthened in electronically excited states by comparison with those in ground state. Hence, we have confirmed again that intermolecular hydrogen bonds between C102 chromophore and aqueous solvents are strengthened not cleaved upon electronic excitation, which is in accordance with Zhao's works.
Ensuring safe water supply for communities across the United States is a growing challenge due to aging infrastructure, impaired source water, strained community finances, etc. In 2019, about 6% of public water utilities in the U.S. had a health-based violation. Due to the high risk of exposure to various contaminants in drinking water, point-of-use (POU) drinking water treatment is rapidly growing in popularity in the U.S. and beyond. POU treatment technologies include various combinations of string-wound sediment filters, activated carbon, modified carbon, ion exchange and redox media filters, reverse osmosis membranes, and ultraviolet lamps depending on the contaminants of concern. While the technologies are well-proven, highly commoditized, and cost-effective, most systems offer little in the way of real-time performance monitoring or interactive technology like other smart home appliances (e.g., thermostats, smoke detectors, doorbells, etc.). Herein, we review water quality regulations and violations in the U.S. as well as state-of-the-art POU technologies and systems with an emphasis on their effectiveness at removing the contaminants most frequently reported in notices of violations. We conclude by briefly reviewing emerging smart water technologies and the needs for advances in the state-of-the-art technologies. The smartness of commercially available POU water filters is critiqued and a definition of smart water filter is proposed.
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