1,089 research outputs found
Van der Waals Materials for Atomically-Thin Photovoltaics: Promise and Outlook
Two-dimensional (2D) semiconductors provide a unique opportunity for
optoelectronics due to their layered atomic structure, electronic and optical
properties. To date, a majority of the application-oriented research in this
field has been focused on field-effect electronics as well as photodetectors
and light emitting diodes. Here we present a perspective on the use of 2D
semiconductors for photovoltaic applications. We discuss photonic device
designs that enable light trapping in nanometer-thickness absorber layers, and
we also outline schemes for efficient carrier transport and collection. We
further provide theoretical estimates of efficiency indicating that 2D
semiconductors can indeed be competitive with and complementary to conventional
photovoltaics, based on favorable energy bandgap, absorption, external
radiative efficiency, along with recent experimental demonstrations. Photonic
and electronic design of 2D semiconductor photovoltaics represents a new
direction for realizing ultrathin, efficient solar cells with applications
ranging from conventional power generation to portable and ultralight solar
power.Comment: 4 figure
High Photovoltaic Quantum Efficiency in Ultrathin van der Waals Heterostructures
We report experimental measurements for ultrathin (< 15 nm) van der Waals
heterostructures exhibiting external quantum efficiencies exceeding 50%, and
show that these structures can achieve experimental absorbance > 90%. By
coupling electromagnetic simulations and experimental measurements, we show
that pn WSe2/MoS2 heterojunctions with vertical carrier collection can have
internal photocarrier collection efficiencies exceeding 70%.Comment: ACS Nano, 2017. Manuscript (25 pages, 7 figures) plus supporting
information (7 pages, 4 figures
Electrical Control of Linear Dichroism in Black Phosphorus from the Visible to Mid-Infrared
The incorporation of electrically tunable materials into photonic structures
such as waveguides and metasurfaces enables dynamic control of light
propagation by an applied potential. While many materials have been shown to
exhibit electrically tunable permittivity and dispersion, including transparent
conducting oxides (TCOs) and III-V semiconductors and quantum wells, these
materials are all optically isotropic in the propagation plane. In this work,
we report the first known example of electrically tunable linear dichroism,
observed here in few-layer black phosphorus (BP), which is a promising
candidate for multi-functional, broadband, tunable photonic elements. We
measure active modulation of the linear dichroism from the mid-infrared to
visible frequency range, which is driven by anisotropic quantum-confined Stark
and Burstein-Moss effects, and field-induced forbidden-to-allowed optical
transitions. Moreover, we observe high BP absorption modulation strengths,
approaching unity for certain thicknesses and photon energies
Arduino based Dual Axis Smart Solar Tracker
Solar energy is rapidly advancing as an important means of renewable energy resource. It is radiant light and heat from the Sun that is harnessed using a range of ever-evolving technologies such as solar heating, photovoltaic, solar thermal energy, solar architecture, molten salt power plants and artificial photosynthesis. Trackers direct solar panels or modules toward the sun. These devices change their orientation throughout the day to follow the sun's path to maximize energy capture. The use of solar trackers can increase electricity production by around a third, and some claim by as much as 40% in some regions, compared with modules at a fixed angle. In any solar application, the conversion efficiency is improved when the modules are continually adjusted to the optimum angle as the sun traverses the sky. This paper presents the designing of a solar tracking system which is based on Arduino UNO and which provides movement of solar panel in the direction of maximum sun light incident. As a result of which we get more efficient system which is compact, low cost as well as easy to use
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