Polarization-insensitive Absorption Enhancement Research Articles

Polarization-insensitive broadband absorption enhancement with few-layer MoS2 film

A polarization-insensitive broadband absorber with few-layer molybdenum disulfide (MoS2) films is designed. The proposed absorber is composed of a dielectric antireflective coating and an ultrathin MoS2 film deposited on a metal square resonator array backed with a metallic mirror. It is shown that the polarization-insensitive absorption enhancement in the ultrathin MoS2 film is realized in the visible region for normally incident light. The distributions of electric field intensity at several resonant wavelengths are investigated to intuitively disclose the physical origin of such phenomenon. Moreover, the optical performances, i.e. the absorption spectra versus the change of incident angle for both polarizations, the angular sensitivity of the integrated absorption and the short-circuit current density, are simulated and examined, all of which outperforms the referenced planar structure. It is believed that the conclusions provide a promising way to design and fabricate ultrathin MoS2 solar cells and other novel optoelectronic devices.

Design of plasmonic backcontact nanogratings for broadband and polarization-insensitive absorption enhancement in thin-film solar cell

We discuss the rules for designing nanostructured plasmonic backcontact of thin-film crystalline silicon solar cells using two-dimensional finite-difference time-domain (2D-FDTD) method. A novel efficient quasi-periodic plasmonic nanograting is designed. Numerical calculations demonstrate that broadband and polarization-insensitive absorption enhancement is achieved by the proposed structure which is based on a supercell geometry containing N subcells in each of which there is one Ag nanowire deposited on the backcontact of the solar cell. The proposed structure offers the possibility of controlling the number and location of photonic and plasmonic modes and outperforms the periodic plasmonic nanogratings which only utilize plasmonic resonances. We start by tuning the plasmonic mode of one subcell and then construct the supercell based on the final design of the subcell. Our findings show that with a proper choice of key parameters of the nanograting, several photonic and plasmonic modes can be excited across the entire spectral region where crystalline silicon (c-Si) is absorbing. The absorption enhancement is significant, particularly in the long wavelength region where c-Si is weakly absorbing.

Quasiperiodic plasmonic concentrators for enhanced light absorption in ultra-thin film solar cells

ABSTRACTThis report will demonstrate broadband, wide-angle, and polarization-insensitive absorption enhancement in ultra-thin films resting on metal substrates that have been etched with arrays of shallow sub-wavelength cylindrical holes. Absorption enhancement will be studied as a function of array geometry, with particular emphasis given to quasiperiodic arrays (a class of deterministic aperiodic arrays that were originally developed to tessellate 2-D planes with regular polygons). Through simulations and experimental data, it was found that absorption enhancement is heavily dependent on the rotational symmetry of the pattern of holes, as well as the inter-hole distance.

Polarization-Insensitive Metal–Semiconductor–Metal Nanoplasmonic Structures for Ultrafast Ultraviolet Detectors

We propose a theoretical design principle of polarization-insensitive metal–semiconductor–metal (MSM) structure for ultraviolet photodetectors based on one-dimensional nanogratings. Because the Fabry–Perot cavity modes supported by a 100-nm-thick ZnO layer with nanostructures for transverse electric and transverse magnetic polarized incidence overlap with each other, a polarization-insensitive absorption enhancement for the ZnO layer at UV wavelengths is achieved, which can be implemented as a nano-interdigitated electrode to address a long-existing limitation between the speed and the responsivity for conventional MSM photodetectors.

Plasmonic concentrators for enhanced light absorption in ultrathin film organic photovoltaics

We report on experimental absorption enhancement in 24 and 150-nm-thick bulk heterojunctions of the conducting polymer poly(3-hexylthiophene) and the fullerene (6,6)-phenyl C61 butyric acid methyl ester. By using periodic and quasiperiodic hole arrays as nanoengineered plasmonic concentrators milled in a silver film, a spectrally broad, omnidirectional, and polarization-insensitive absorption enhancement is observed over that of a reference layer deposited on a flat film. As the result of increased absorption, an enhancement in the polymer fluorescence intensity is also observed. This demonstrates the potential of plasmonic concentrators for improved energy harvesting in ultrathin film solar cells.