The narrow indirect bandgap of Si hinders the full absorption and utilization of the solar light. Energy band engineering to the Si based photovoltaic devices is essential to address this problem. Here we report the fabrication of ZnSe nanoribbon (ZnSeNR)/Si nanowire (SiNW) p–n heterojunction arrays by directly growing or simply drop-casting the p-type ZnSeNRs on highly aligned n-type SiNW arrays. Phosphorus (P) was used as dopant to achieve robust p-type doping in the ZnSe nanostructures with a hole concentration as high as 6.5 × 1018 cm−3. Thanks to the matched bandgap and the light trapping arising from the one-dimensional (1D) array structure, the heterojunction arrays exhibited improved light absorption, particularly in the blue/UV wavelength range. Moreover, by taking advantage of the ohmic contact between graphene and p-ZnSeNR, heterojunction array solar cells with graphene transparent electrode were fabricated, giving rise to a power conversion efficiency of ∼0.78% under AM 1.5G illumination. It was found that the surface passivation to the SiNW array played an important role in determining the device performance; an efficiency up to 2.27% was obtained after surface modification with methyl groups. Our results demonstrate the heterojunction arrays, together with the graphene transparent electrodes, could be promising candidates for high-performance and low-cost photovoltaic applications.
The rapid development of ocean exploration and underwater robot technology has put forward new requirements for underwater sensing methods, which can be used for hydrodynamic characteristics perception, underwater target tracking, and even underwater cluster communication. Here, inspired by the specialized undulated surface structure of the seal whisker and its ability to suppress vortex-induced vibration, a multidirectional hydrodynamic sensor based on biomimetic whisker array structure and magnetic 3D self-decoupling theory is introduced. The magnetic-based sensing method enables wireless connectivity between the magnetic functional structures and electronics, simplifying device design and endowing complete watertightness. The 3D self-decoupling capability enables the sensor, like a seal or other organisms, to perceive arbitrary whisker motions caused by the action of water flow without complex calibration and additional sensing units. The whisker sensor is capable of detecting a variety of hydrodynamic information, including the velocity (RMSE < 0.061 m s −1 ) and direction of the steady flow field, the frequency (error < 0.05 Hz) of the dynamic vortex wake, and the orientation (error < 7°) of the vortex wake source, demonstrating its extensive potential for underwater environmental perception and communication, especially in deep sea conditions.
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