As an effort to identify van der Waals heterostructures for efficient excitonic solar cell application, high-throughput computational screening was carried out to study the band alignments of 1540 vertical heterostructures formed by 56 two-dimensional semiconducting/insulating materials. More than 90 heterostructures with estimated power conversion efficiency (PCE) higher than 15% have been identified, of which 17 heterostructures are predicted to have PCE higher than the best value (20%) reported or proposed in the literature.

Using the many-body perturbation GW theory, we study the quasiparticle conduction-band offsets of phosphorene, a two-dimensional atomic layer of black phosphorus, and transition-metal dichalcogenides (TMDs). The calculated large exciton binding energies of phosphorene and TMDs indicate that their type-II heterostructures are suitable for excitonic thin-film solar cell applications. Our results show that these heterojunctions have a potential maximum power conversion efficiency of up to 12%, which can be further enhanced up to 20% by strain engineering.

State-of-the-art chemical sensors based on covalent organic frameworks (COFs) are restricted to the transduction mechanism relying on luminescence quenching and/or enhancement. Herein, we present an alternative methodology via a combination of in situ-grown COF films with interdigitated electrodes utilized for capacitive benzene detection. The resultant COF-based sensors exhibit highly sensitive and selective detection at room temperature toward benzene vapor over carbon dioxide, methane, and propane. Their benzene detection limit can reach 340 ppb, slightly inferior to those of the metal oxide semiconductor-based sensors, but with reduced power consumption and increased selectivity. Such a sensing behavior can be attributed to the large dielectric constant of the benzene molecule, distinctive adsorptivity of the chosen COF toward benzene, and structural distortion induced by the custom-made interaction pair, which is corroborated by sorption measurements and density functional theory (DFT) calculations. This study provides new perspectives for fabricating COF-based sensors with specific functionality targeted for selective gas detection.

It is shown experimentally that carbon incorporation into zinc oxide (ZnO) nanowires (NWs) plays a crucial role in determining the NWs' fluorescence and photoluminescence properties. Through intentional adjustment of chemical vapor deposition growth parameters to allow for carbon incorporation, the ZnO NWs' fluorescence under ultraviolet excitation can be varied controllably from green to orange‐red. X‐ray photoelectron spectroscopy, X‐ray absorption spectroscopy, and transmission electron microscopy correlate carbon incorporation to a systematic shifting of ZnO NWs' fluorescence toward higher wavelengths. This is consistent with a previous theoretical prediction of orange‐red fluorescence arising from a carbon‐related defect within ZnO. In the present work, further computational results from simulation of high carbon content within the ZnO lattice yield additional carbon‐related defect species as possible origins of orange‐red fluorescence. Furthermore, the extent of simulated band gap energies can help explain the broad visible fluorescence spectrum from carbon incorporated ZnO. Additional experiments involving plasma etching and oxygen annealing agree with the inferences of carbon‐related defects as a source of variable visible‐light emissions.

Doping nitrogen (N) into TiO2 is one of the promising ways to extend the photocatalytic activity into the visible-light range, enabling to harvest more solar energy. In this study, we realize a high concentration of N incorporated into the anatase TiO2 films on indium tin oxide substrates. The band gap of TiO2 with a high N substitutional doping is reduced to 1.91 eV, showing a much improved photocatalytic reactivity, as supported by the degrading methyl orange solution radiated with visible light. First-principles calculations further suggest that the form of dominant defects evolves from the substitution of N (NO) to the coexistence of NO and oxygen vacancies (OV) when the N-doping concentration is increased, which leads to the reduction of band gap in the visible-light range and more delocalized charge distribution. Our results demonstrate a novel synthesis route that can realize a high concentration of N substitutional doping in TiO2 films and provide an improved understanding of enhanced visible-light photocatalytic performance of N-doped TiO2.