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Commercialization of lead halide perovskite-based devices is hindered by their instability towards environmental conditions. In particular, water promotes fast decomposition, leading to a drastic decrease in device performance. Integrating water-splitting active species within ancillary layers to the perovskite absorber might be a solution to this, as they could convert incoming water into oxygen and hydrogen, preserving device performance. Here, we suggest that a CuSCN nanoplatelete/p-type semiconducting polymer composite, combining hole extraction and transport properties with water oxidation activity, transforms incoming water molecules and triggers the in situ p-doping of the conjugated polymer, improving transport of photocharges. Insertion of the nanocomposite into a lead perovskite solar cell with a direct photovoltaic architecture causes stable device performance for 28 days in high-moisture conditions. Our findings demonstrate that the engineering of a hole extraction layer with possible water-splitting additives could be a viable strategy to reduce the impact of moisture in perovskite devices. The poor environmental stability of lead halide perovskites limits their performance in solar cells. Here, a CuSCN nanoplateletes/p-type semiconducting polymer composite layer enables the stable performance of a solar cell for 28 days in high-moisture conditions, attributed to water splitting.

Summary Promoting solar fuels as a viable alternative to hydrocarbons calls for technologies that couple efficiency, durability, and low cost. In this work we elucidate how hybrid organic-inorganic systems employing hybrid photocathodes (HPC) and perovskite solar cells (PSC) could eventually match these needs, enabling sustainable and clean hydrogen production. First, we demonstrate a system comprising an HPC, a PSC, and a Ru-based oxygen evolution catalyst reaching a solar-to-hydrogen (STH) efficiency above 2%. Moving from this experimental result, we elaborate a perspective for this technology by adapting the existing models to the specific case of an HPC-PSC tandem. We found two very promising scenarios: one with a 10% STH efficiency, achievable using the currently available semiconducting polymers and the widely used methylammonium lead iodide (MAPI) PSC, and the other one with a 20% STH efficiency, requiring dedicated development for water-splitting applications of recently reported high-performing organic semiconductors and narrow band-gap perovskites., Graphical abstract, Highlights • 2% STH efficiency with a hybrid photocathode/perovskite solar cell tandem system • Multi-variable optimization tool used to find the optimal parameters to maximize STH • Optimized photocathode parameters are found in order to reach the 10% STH goal • Long-term scenario with 20% STH is predicted for hybrid organic tandem systems, Chemistry; Chemical engineering; Catalysis; Electrochemistry

Molybdenum sulfide emerged as promising hydrogen evolution reaction (HER) electrocatalyst thanks to its high intrinsic activity, however its limited active sites exposure and low conductivity hamper its performance. To address these drawbacks, the non-equilibrium nature of pulsed laser deposition (PLD) is exploited to synthesize self-supported hierarchical nanoarchitectures by gas phase nucleation and sequential attachment of defective molybdenum sulfide clusters. The physics of the process are studied by in situ diagnostics and correlated to the properties of the resulting electrocatalyst. The as-synthesized architectures have a disordered nanocrystalline structure, with nanodomains of bent, defective S-Mo-S layers embedded in an amorphous matrix, with excess sulfur and segregated molybdenum particles. Oxygen incorporation in this structure fosters the creation of amorphous oxide/oxysulfide nanophases with high electrical conductivity, enabling fast electron transfer to the active sites. The combined effect of the nanocrystalline pristine structure and the surface oxidation enhances the performance leading to small overpotentials, very fast kinetics (35.1 mV dec-1 Tafel slope) and remarkable long-term stability for continuous operation up to -1 A cm-2. This work shows possible new avenues in catalytic design arising from a non-equilibrium technique as PLD and the importance of structural and chemical control to improve the HER performance of MoS-based catalysts.

An important field to improve solar cell efficiency is the optimization of the antireflection coating (ARC) to allow more light to be converted; from a theoretical point of view this could increase the solar cell efficiency of 0.5%. Different ARC designs have been investigated, the most promising approaches are based on multi layers or gradient index approaches. These approaches have been theoretically and experimentally optimized to increase the photocurrent in the spectral range 300-1880 nm. Experimental results show that the solar cell efficiency can be increased of 0.5% both on thin and standard CESI space solar cells having 30% BOL efficiency.

Photoelectrochemical H2 production through hybrid organic/inorganic interfaces exploits the capability of polymeric absorbers to drive photo-induced electron transfer to an electrocatalyst in a water environment. Photoelectrode architectures based on solution-processed organic semiconductors are now emerging as low-cost alternatives to crystalline inorganic semiconductors based on Si, oxides and III–V alloys. In this work, we demonstrate that the stability of a hybrid organic/inorganic photocathode, employing a P3HT:PCBM blend as photoactive material, can be considerably improved by introducing an electrochemically stable WO3 hole selective layer, paired with a TiO2 electron selective layer. This hybrid photoelectrode exhibits a photocurrent of 2.48 mA cm−2 at 0 VRHE, +0.56 VRHE onset potential and a state-of the art operational activity of more than 10 hours. This work gives the perspective that photoelectrodes based on organic semiconductors, coupled with proper inorganic selective contacts, represent a sound new option for the efficient and durable photoelectrochemical conversion of solar energy into fuels.

Quasi-1D-hyperbranched TiO

Fast switchable electrochromic devices can be realized through the implementation of engineered quasi-1D WO3 nanostructures. Three different batches of WO3 working electrodes have been fabricated by controlling the self-assembly process of the evaporating WO3 clusters to build up a forest of high aspect-ratio tree-like nanostructures that conjugate the peculiar features of 1D nanoarchitectures (which are characterized by relatively fast electron transport) and those ones of isotropic mesoporous films (which are characterized by relatively high surface area). Their unique morphological prerogatives have been favorably exploited to achieve good coloration efficiency (65 cm2 C−1 at 660 nm) and exceptionally short coloration time (

Arrays of hyperbranched high aspect ratio mesostructures are grown by pulsed laser deposition through a self-assembly process from the gas phase. These hierarchical arrays are successfully used as photoanodes for the photoelectrochemical splitting of water, exhibiting an onset potential as low as 0.4 V vs. RHE and saturation current densities up to 1.85 mA cm−2 at 0.8 V vs. RHE. While the latter is similar to the state of the art values for WO3 nanostructured photoanodes, both the onset and saturation voltages are significantly lower than any other reported values. This peculiar behavior is attributed to the hyperbranched structure and to its excellent optical and electronic properties.

Photoelectrochemical H

Graphite conductive vertical microchannels, fabricated by femtosecond laser treatment, are proposed as distributed electrodes in defect-engineered (“black”) single-crystal diamond cathodes for innovative solar cells. Energy conversion is based on photon-enhanced thermionic emission, where the reduction of the cathode series resistance is crucial to preserve conversion efficiency. Process yield higher than 80% and resistivity as low as 0.75 ± 0.15 Ω cm were achieved by the optimization of laser parameters and the use of a multi-pass writing technique. A 100 × 100 array of graphite electrodes was integrated in a diamond-based cathode prototype, reducing the series resistance of more than 10 orders of magnitude with respect to bulk diamond.

Quasi-1D-hyperbranched TiO2 nanostructures are grown via pulsed laser deposition and sensitized with thin layers of CdS to act as a highly efficient photoelectrochemical photoanode. The device properties are systematically investigated by optimizing the height of TiO2 scaffold structure and thickness of the CdS sensitizing layer, achieving photocurrent values up to 6.6 mA cm-2 and reaching saturation with applied biases as low as 0.35 VRHE. The high internal conversion efficiency of these devices is to be found in the efficient charge generation and injection of the thin CdS photoactive film and in the enhanced charge transport properties of the hyperbranched TiO2 scaffold. Hence, the proposed device represents a promising architecture for heterostructures capable of achieving high solar-to-hydrogen efficiency.

Nanoscale periodic texturing on polycrystalline CVD diamond surface was performed to obtain a significant increase in optical absorptance to visible and near-infrared radiation. Surface texturing, obtained by the use of fs-laser ultrashort pulses, has been demonstrated to induce a controlled periodicity of ripples of about 170 nm and length of several µm, able to drastically increase the diamond capability of interacting with solar radiation from its intrinsic visible blindness. Ultraviolet and visible Raman spectroscopy has been used to confirm the absence of non-diamond phases resulting from the process for the fs-laser-textured sample. Moreover, here we investigate the optical properties in the range 200 nm–25 µm. Absorbance of fs-laser-textured CVD diamond is considerably higher than the untreated one at every wavelength, resulting in a remarkable increase in the emittance: It points out the need for an optimization of process parameters to enhance the selective absorption capability.