Photoelectrochemical (PEC) fuel synthesis depends on the intermittent solar intensity of the diurnal cycle and ceases at night. Here, an integrated device that does not only possess PEC water splitting functionality, but also operates as an electrolyzer in the nocturnal period to improve the overall capacity factor is described. The bifunctional system is based on an “artificial leaf” tandem PEC architecture that contains an inverse‐structure lead halide perovskite protected by a graphite epoxy/parylene‐C coating (conferring 96 h stability of operation in water), and a porous BiVO4 semiconductor. The light‐absorbers are interfaced with a H2 evolution catalyst (Pt) and a Co‐based water oxidation catalyst, respectively, which can also be directly driven by electricity. Thus, the device can operate in PEC mode during irradiation and switch to an electricity‐powered mode in the dark through bypassing of the semiconductor configuration. The bifunctional perovskite‐BiVO4 tandem provides a solar‐to‐hydrogen efficiency of 1.3% under simulated solar irradiation and an onset for water electrolysis at 1.8 V. The compact design and low cost of the proposed device may provide an advantage over other technologies for round‐the‐clock fuel production.

Ringe um einen Draht: Neuartige hierarchische Heterostrukturen, die durch radiale Abscheidung von InAs auf GaAs‐Nanodrähten mit nichtplanaren Seitenwänden entstehen, führen zur Bildung von InAs‐Nanoringen. Bei dem transmissionselektronenmikroskopisch aufgeklärten Bildungsmechanismus spielt die aufgrund von Kapillareffekten bevorzugte Keimbildung von InAs an konkaven Bereichen der GaAs‐Oberfläche eine Rolle.

We present multiplexer methodology and hardware for nanoelectronic device characterization. This high-throughput and scalable approach to testing large arrays of nanodevices operates from room temperature to milli-Kelvin temperatures and is universally compatible with different materials and integration techniques. We demonstrate the applicability of our approach on two archetypal nanomaterialsgraphene and semiconductor nanowiresintegrated with a GaAs-based multiplexer using wet or dry transfer methods. A graphene film grown by chemical vapor deposition is transferred and patterned into an array of individual devices, achieving 94% yield. Device performance is evaluated using data fitting methods to obtain electrical transport metrics, showing mobilities comparable to nonmultiplexed devices fabricated on oxide substrates using wet transfer techniques. Separate arrays of indium-arsenide nanowires and micromechanically exfoliated monolayer graphene flakes are transferred using pick-and-place techniques. For the nanowire array mean values for mobility μ FE = 880/3180 cm 2 V −1 s −1 (lower/upper bound), subthreshold swing 430 mV dec −1 , and on/off ratio 3.1 decades are extracted, similar to nonmultiplexed devices. In another array, eight mechanically exfoliated graphene flakes are transferred using techniques compatible with fabrication of two-dimensional superlattices, with 75% yield. Our results are a proof-ofconcept demonstration of a versatile platform for scalable fabrication and cryogenic characterization of nanomaterial device arrays, which is compatible with a broad range of nanomaterials, transfer techniques, and device integration strategies from the forefront of quantum technology research.

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