Stable solar water splitting with wettable organic-layer-protected silicon photocathodes

Protective layers are essential for Si-based photocathodes to achieve long-term stability. The conventionally used inorganic protective layers, such as TiO₂, need to be free of pinholes to isolate Si from corrosive solution, which demands extremely high-quality deposition techniques. On the other hand, organic hydrophobic protective layers suffer from the trade-off between current density and stability. This paper describes the design and fabrication of a discontinuous hybrid organic protective layer with controllable surface wettability. The underlying hydrophobic layer induces the formation of thin gas layers at the discontinuous pores to isolate the electrolyte from Si substrate, while allowing Pt co-catalyst to contact the electrolyte for water splitting. Meanwhile, the surface of this organic layer is modified with hydrophilic hydroxyl groups to facilitate bubble detachment. The optimized photocathode achieves a stable photocurrent of 35 mA/cm² for over 110 h with no trend of decay.

Preparation of inorganic protective layers for photoelectrodes requires high-quality deposition techniques. Here, the authors report a spin-coated organic protective layer that enables Si photocathodes to realize stable solar water splitting.

Large-Scale Fabrication of Silicon Nanowires for Solar Energy Applications

The development of silicon (Si) materials during past decades has boosted up the prosperity of the modern semiconductor industry. In comparison with the bulk-Si materials, Si nanowires (SiNWs) possess superior structural, optical, and electrical properties and have attracted increasing attention in solar energy applications. To achieve the practical applications of SiNWs, both large-scale synthesis of SiNWs at low cost and rational design of energy conversion devices with high efficiency are the prerequisite. This review focuses on the recent progresses in large-scale production of SiNWs, as well as the construction of high-efficiency SiNW-based solar energy conversion devices, including photovoltaic devices and photo-electrochemical cells. Finally, the outlook and challenges in this emerging field are presented.

Silicon nanowire heterostructures for advanced energy and environmental applications: a review

Semiconductor nanowires (NWs), in particular Si NWs, have attracted much attention in the last decade for their unique electronic properties and potential applications in several emerging areas. With the introduction of heterostructures (HSs) on NWs, new functionalities are obtained and the device performance is improved significantly in many cases. Due to the easy fabrication techniques, excellent optoelectronic properties and compatibility of forming HSs with different inorganic/organic materials, Si NW HSs have been utilized in various configurations and device architectures. Herein, we review the recent developments in Si NW HS-based devices including the fabrication techniques, properties (e.g., light emitting, antireflective, photocatalytic, electrical, photovoltaic, sensing etc) and related emerging applications in energy generation, conversion, storage, and environmental cleaning and monitoring. In particular, recent advances in Si NW HS-based solar photovoltaics, light-emitting devices, thermoelectrics, Li-ion batteries, supercapacitors, hydrogen generation, artificial photosynthesis, photocatalytic degradation of organic dyes in water treatment, chemical and gas sensors, biomolecular sensors for microbial monitoring etc have been addressed in detail. The problems and challenges in utilizing Si NW HSs in device applications and the key parameters to improve the device performance are pointed out. The recent trends in the commercial applications of Si NW HS-based devices and future outlook of the field are presented at the end.

The diameter-dependent photoelectrochemical performance of silicon nanowires

We demonstrate the first systematic study of the diameter-dependent photoelectrochemical performance of single silicon nanowires within a broad size range from 200 to 2000 nm.