Black silicon solar thin-film microcells integrating top nanocone structures for broadband and omnidirectional light-trapping

Droplet manipulation on a structured shape memory polymer surface

While methods for dynamic tuning of surface wettability to manipulate water droplets have been widely explored for many applications including digital microfluidics, those based on dynamically changeable surface morphology have remained challenging to achieve. In this work, we present a structured shape memory polymer (SMP) surface which shows dynamically tunable surface wettability through changeable surface morphology in order to manipulate water droplets. The structured SMP surface involves a SMP pillar array consisting of nanotextured small and large pillars which can change its morphology between permanent and temporary shapes upon thermomechanical loading. Specifically, the structured SMP surface dynamically creates a surface morphological gradient and changes its surface wettability during thermally induced shape recovery of the SMP pillar array. Different wetting characteristics of the structured SMP surface between permanent and temporary shapes are theoretically predicted and experimentally verified. Based on these measured wetting characteristics, the structured SMP surface is designed to demonstrate that the morphological difference between two shapes under a water droplet overcomes contact angle hysteresis, resulting in driving a water droplet, when combined with the thermal Marangoni effect.

Lithography-free wide-angle antireflective self-cleaning silicon nanocones

Low-cost, wideband, and wide-angle antireflective layers are of prime importance to photovoltaic and other optoelectronic applications. We report a novel fabrication methodology of random textured silicon nanocones (SiNCs) array through metal-assisted chemical etching combined with oxidation. The optical properties of the fabricated structure are studied theoretically and experimentally. The random textured SiNCs array showed very promising broadband antireflective properties through the entire visible wavelength range at different incident angles up to ±60°. In addition, the nanostructures inherently could become self-cleaning due to the high contact angle. This random cheap textured SiNCs array increases the absorption efficiency of photodetectors and reduces its cost.

Plasmonic near-touching titanium oxide nanoparticles to realize solar energy harvesting and effective local heating

Through the excitation of plasmon resonance, the energy of plasmonic nanoparticles either reradiates through light scattering or decays into energetic electrons (absorption). The plasmon-induced absorption can greatly enhance the efficiency of solar energy harvesting, local heating, photodetection and photocatalysis. Here, we demonstrate that heavily self-doped titanium oxide nanoparticles (TiO1.67 analogue arising from oxygen vacancies in rutile TiO2) with the plasmon resonance dominated by an interband transition shows strong absorption to build a broadband perfect absorber in the wavelength range from 300 to 2000 nm covering the solar irradiation spectrum completely. The absorptivity of the fabricated array is greater than 90% in the whole spectral range. And the broadband and strong absorption is due to the plasmon hybridization and hot spot generation from near-touching TiO1.67 nanoparticles with different sizes. What is more, the local heating of a TiO1.67 nanoparticle layer is fast and effective. The temperature increases quickly from 30 °C to 80 °C within 200 seconds. This local heating can realize rapid solar-enabled evaporation which can find applications in large-scale distillation and seawater desalination. These findings actually open a pathway for applications of these newly developed plasmonic materials in the energy and environment fields.