To guide the design of plasmonic solar cells, theoretical investigation of core (metal)-shell (dielectric) nanoparticles for light absorption enhancement in thin film Si solar cells is performed. In contrast to the reported simulations and experimental results that rear-located surface plasmon on bare metallic nanoparticles is preferred, the core-shell nanoparticles demonstrate better performance when surface plasmon is located in front of a solar cell. This has been attributed to the enhanced forward scattering with vanishing backward scattering preserved over a wide spectral range in core-shell nanoparticles. This work provides a concept to achieve enhanced forward scattering with weakened backward scattering in plasmonic thin film solar cells.

Ta3N5 is a promising semiconductor for solar-driven photocatalytic or photoelectrochemical (PEC) water splitting. However, the lack of an in-depth understanding of its intrinsic defect properties limits further improvement of its performance. In this study, comprehensive spectroscopic characterizations are combined with theoretical calculations to investigate the defect properties of Ta3N5. The obtained electronic structure of Ta3N5 reveals that oxygen impurities are shallow donors, while nitrogen vacancies and reduced Ta centers (Ta3+) are deep traps. The Ta3+ defects are identified to be most detrimental to the water splitting performance because their energetic position lies below the water reduction potential. Based on these findings, a simple H2O2 pretreatment method is employed to improve the PEC performance of the Ta3N5 photoanode by reducing the concentration of Ta3+ defects, resulting in a high solar-to-hydrogen conversion efficiency of 2.25%. The fundamental knowledge about the defect properties of Ta3N5 could serve as a guideline for developing more efficient photoanodes and photocatalysts.

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Realization of the half-metallicity in graphene is of crucial importance in all-carbon organic spintronic nanodevices. Here, using first-principles calculations, we predicted the existence of half-metallicity in porphin-decorated graphene nanoribbons based on the synthesized porphin-decorated graphene [He et al., Nat. Chem. 9, 33–38 (2017)]. The configurations are constructed by coupling porphin molecules to one side of three different graphene nanoribbons: zigzag, sawtooth, and armchair graphene nanoribbons. We found that the porphin-decorated zigzag graphene nanoribbons (ZGNRs) exhibit half-metallicity, where their bandgaps are fixed at ∼0.3 eV for the gapped spin channel regardless of the variation of the ribbon width. Different from ZGNR, porphin-decorated sawtooth graphene nanoribbons exhibit ferromagnetic semiconducting properties, and for the armchair graphene nanoribbons, porphin modification only influences their bandgaps. Our findings open an avenue to the graphene-based electronic and spintronic devices.