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International audience; A metal–insulator–semiconductor (MIS) structure based on an inhomogeneous junction has been recently proven to be highly efficient at photoelectrochemical (PEC) water oxidation. Engineering the surrounding layer of the MIS nanojunction is crucial to maximizing the photovoltage. Specifically, for an n-type photoanode, a high work-function material is required to create a large Schottky barrier that assists the hole transfer to oxidize water while blocking the electron transfer. Normally, the surrounding layer is a native oxidized phase of the metal layer that forms unintentionally. Herein, we demonstrate the use of copper(I) thiocyanate (CuSCN), a transparent p-type coordination polymer semiconductor with a high work function, to specifically surround the n-Si/SiOx/Cu nanojunctions, resulting in an increased effective barrier height from 0.71 to 1.03 eV. This phenomenon, known as the pinch-off effect, is also applied to improve the performance of the planar n-Si/SiOx/Cu electrode via a PEC dissolution method that creates an inhomogeneous surface covered with CuOx. The Cu/CuSCN nanojunction still shows superior characteristics due to the favorable energetics of CuSCN. This work shows a rational route for engineering the surrounding layer to improve the performance of Si-based MIS photoelectrodes, enabled by the facile chemistry of coordination polymers

The solid-state mechanochemical reactions under ambient conditions of CuSCN and Zn(SCN)2 resulted in two novel materials: partially Zn-substituted α-CuSCN and a new phase CuxZny(SCN)x+2y. The reactions take place at the labile S-terminal, and both products show melting and glass transition behaviors. The optical band gap and solid-state ionization potential can be adjusted systematically by adjusting the Cu/Zn ratio. Density functional theory calculations also reveal that the Zn-substituted CuSCN structure features a complementary electronic structure of Cu 3d states at the valence band maximum and Zn 4s states at the conduction band minimum. This work shows a new route to develop semiconductors based on coordination polymers, which are becoming technologically relevant for electronic and optoelectronic applications.

Zr-based UiO-66 metal-organic framework (MOF) is one of the most studied MOFs with a wide range of potential applications. While UiO-66 is typically synthesized as a microcrystalline solid, we employ a particle downsizing strategy to synthesize UiO-66 as fluid gel with unique rheological properties, which allows the solution-based processing as sub-100 nm films and enhances the electrical conductivity of its pristine structure. Film thicknesses ranging from 40 to 150 nm could be achieved by controlling the spin-coating parameters. The generality of the method is also demonstrated for other Zr-based MOFs including MOF-801 and MOF-808. The impact of particle size and film thickness at the nanoscale on electrical properties of UiO-66 is shown to realize new features that are distinct from those of the bulk powder phase. An electrical insulator UiO-66 shows a significant increase in the electrical conductivity (10-5 S cm-1 compared to 10-7 S cm-1 in the bulk powder phase) when the 10 nm particles are distributed on the substrate with a thickness less than 100 nm. The findings establish a new route for processing of MOF materials as thin films with fine-tuned thickness and offer a new perspective for transport properties of Zr-based MOFs without structural modification.

The solid-state mechanochemical reactions under ambient conditions of CuSCN and Zn(SCN)2 resulted in two novel materials: partially Zn-substituted α-CuSCN and a new phase CuxZny(SCN)x+2y. The reactions take place at the labile S-terminal, and both products show melting and glass transition behaviors. The optical band gap and solid-state ionization potential can be adjusted systematically by adjusting the Cu:Zn ratio. Density functional theory calculations also reveal that the Zn-substituted CuSCN structure features a complementary electronic structure of Cu 3d states at the valence band maximum (VBM) and Zn 4s states at the conduction band minimum (CBM). This work shows a new route to develop semiconductors based on coordination polymers which are becoming technologically relevant for electronic and optoelectronic applications.

We report the synthesis of two novel cyclopenta[2,1-b:3,4-b′]dithiophen-4-one monomers containing solubilizing alkyl groups in the peripheral 3,5 positions. Polymerization with (E)-1,2-bis(tributylstannyl)-ethylene under Stille coupling conditions afforded the first reported examples of soluble poly(cyclopentadithiophen-4-one)vinylenes. The resulting polymers absorb in the near-infrared, with a maximum thin film absorbance around 815 nm and have optical band gaps of 1.25 eV. The polymers exhibit promising ambipolar field effect transistor performance, with average saturated mobilities of 0.5 cm2 V–1 s–1 for holes and 0.12 cm2 V–1 s–1 for electrons. The ambipolar transistors operate in both the hole and electron transport regimes in ambient air. Prolonged exposure to ambient atmosphere leads to a gradual loss of the electron transport behavior, with little change observed in the p-type mobility.