Graphene/alpha-tellurene van der Waals heterobilayers: Interlayer coupling and gate-tunable carrier type and Schottky barriers
APPLIED SURFACE SCIENCE
Authors: Liu, Hairui; Gao, Rui; Yang, Jien; Yang, Feng; Wang, Tianxing; Zhang, Zhuxia; Liu, Xuguang; Jia, Husheng; Xu, Bingshe; Ma, Heng
Two-dimensional (2D) graphene/semiconductors van der Waals (vdW) heterostructures possess ultra high carrier mobility and fine mechanical properties, which show potential applications in nanoelectronics. The regulations on interface Schottky barriers and doping concentrations are still important questions. In this work, the electronic properties of graphene/alpha-tellurene (Gr/alpha-Te) van der Waals heterobilayers (vdW HBS) are studied via first-principle calculations. It is found that p-type Schottky contact with a low p-type Schottky barrier height (similar to 0.18 eV) is formed at the graphene-alpha-Te interface. Furthermore, n-type Schottky barrier transforms to p-type when we compress interlayer distance or apply external electric field. Moreover, the hole doping in graphene can be modulated to electron doping via compressing interlayer distance from 3.53 angstrom to 2.70 angstrom or exerting weak negative electric field. These predicted results show that Gr/alpha-Te vdW HBS possesses interlayer-distance and electric-field dependent Schottky barrier height, which is very useful to develop Gr/alpha-Te-based electronic devices.
Highly efficient solar hydrogen production through the use of bifacial photovoltaics and membrane electrolysis
JOURNAL OF POWER SOURCES
Authors: Privitera, S. M. S.; Muller, M.; Zwaygardt, W.; Carmo, M.; Milazzo, R. G.; Zani, P.; Leonardi, M.; Maita, F.; Canino, A.; Foti, M.; Bizzarri, F.; Gerardi, C.; Lombardo, S. A.
The large-scale implementation of solar hydrogen production requires an optimal combination of photovoltaic systems with suitably-designed electrochemical cells, possibly avoiding power electronics for DC-DC conversion, to decrease costs. Here, a stable, solar-driven water splitting system is presented, obtained through the direct connection of a state-of-the-art proton exchange membrane (PEM) electrolyzer to a bifacial silicon heterojunction (SHJ) solar module of three cells in series with total area of 730 cm(2). The bifaciality of the solar module has been optimized through modeling in terms of the number of cells, module height and inclination. During outdoor operation in the standard monofacial configuration, the system is able to produce 3.7 gr of H-2 h(-1)m(-2) with an irradiation of 1000 W m(-2) and a solar-to-hydrogen efficiency (STH) of 11.55%. The same system operating in bifacial mode gives rise to a higher H-2 flux and STH efficiency, reaching values of 4.2 gr of H-2 h(-1)m(-2) and STH of 13.5%. Such a noticeable difference is achieved through the collection of albedo radiation from the ground by the bifacial PV system. The system has been tested outdoors for more than 55 h, exhibiting very good endurance, with no appreciable change in production and efficiency.