Guangyao Su

Broadband absorption enhancement in ultrathin-film solar cells by combining dielectric nanogratings and metallic nanoribbons

Abstract. Optical absorption improvement and cost reduction of thin-film solar cells have been long-time issues. These two aims are achieved simultaneously by combining metallic nanoribbons and dielectric gratings at the front side of ultrathin-film amorphous silicon solar cells. Surface-plasmon-polariton waves excited by the nanoribbons at the long wavelength co-operates with Uller-Zenneck waves and cavity resonances excited by the gratings at the short wavelength with little cross-effect, leading to a complementary absorption enhancement of 31% when compared to planar structure. In addition, this design exhibits wide-angle absorption as well as a high fabrication tolerance. Compared to the previous work combining different mechanisms, this design provides fewer fabrication steps and an easier approach. Moreover, the nanoribbons can be used as a transparent conducting electrode for a low-cost alternative to expensive indium tin oxide thin-film.

Polarization insensitive perfect absorber with nanorod arrays

We propose a polarization insensitive near infrared perfect absorber (PA) based on the localized surface plasmon resonances (LSPRs) of nanorod arrays. Polarization insensitivity of our PA structure is achieved by combining two sets of nanorods with x and y orientation respectively. Study carried out by finite difference time domain (FDTD) method shows absorption rate and the peak wavelength are sensitive to the lattice period both in x and y directions. The nanorods resonance is only slightly impacted by nanorods on its vertical direction. Further research into multiband polarization-insensitive absorber can be expected base on this work.

Absorption enhancement of a-Si thin film solar cells through surface plasmon polaritons and cavity resonance

A back metallic binary-rectangle grating is proposed to realize absorption enhancement through introducing plasmonic modes and cavity resonance modes. The grating contains a secondary grating whose height is optimized. Adding the structure can enhance absorption by a factor of 2.6 at λ = 915 nm and for the wavelengths in the range 550-790 nm, 875-900 nm the absorption is also enhanced.

A Design of a-Si Thin Film Solar Cell with A Dual Grating for Long Wavelength Absorption Enhancement

A structure combined dual diffraction grating is investigated. Great enhancement at the discussed wavelength rang can be seen. The maximum enhancement rate can reach 25 at the wavelength of 950 nm and enhancement is broadband.

The effect of transparent conductive oxides background spacer layer on light trapping in thin film solar cells

The influence of optical absorption in thin film solar cells induced by the transparent conductive oxide (TCO) spacer layer was numerically investigated. The paper results provide a guideline for designing TCO spacer layer.

Broadband light absorption enhancement in thin-film solar cells by combining front dielectric and back metallic gratings

We numerically study the absorption enhancement of amorphous Si (α-Si) solar cells, in which a dual grating structure combining front dielectric grating and back metal grating is proposed to improve light absorption in the 300-900 nm wavelength range. The front dielectric grating scatters the incident light into active layer which can reduce reflection without much energy loss, especially at the short wavelengths. The back metal grating causes the absorption enhancement at long wavelengths due to the excitation of surface plasmon polaritons (SPPs) at the interface of metal/semiconductor and/or photonic modes in the active layer. When these two gratings are combined, a large, broadband absorption enhancement over the entire spectrum can be realized. For better comparison, the flat structure without any gratings is chosen as a reference. In our work, the absorption enhancement of the solar cells with dual gratings is superior to the structures with a front dielectric or back metal grating alone in almost over the entire wavelength range 300-900 nm. For wavelengths in the range 300-900 nm, 72.4% absorptivity is observed for 100-nmthickness flat α-Si solar cell, 76.9% and 75.1% for front and back grating cases, and up to 82.6% for dual grating case at the grating period of 360 nm.

Thin film solar cells based on cavity enhanced grating structure

A cavity enhanced one-dimensional grating structure is proposed to improve the light absorption within the α-Si thin film solar cell. Typically, dielectric or metal structure including gratings is added for the light absorption enhancement. Not only does the structure form the guided modes, and increase the surface area/surface angle, but also the thin film itself forms a cavity allowing light trapping for better absorption. However, the structure is optimized in these two mechanisms separately. In this paper, finite element method (FEM) was used to optimize thicknesses of two cavities and then combine them into a one –dimensional grating structure. Comparing to the flat thin film solar cell, we have get absorption enhancement factors of 1.12 and 1.51 normalized for the AM 1.5 spectrum for 300 nm to 950 nm by the two proposed structures.

Absorption enhancement for solar cells structured with quasi-periodic grating

Solar cells structured with quasi-periodic and periodic gratings are investigated. A broadband great enhancement can be observed. The quasi-periodic grating design is based on Fourier transform.

Hybrid Gratings for Complementary Absorption Enhancement in Ultra-thin Film Solar Cells

Amorphous silicon ultra-thin film solar cells with hybrid plasmonic and dielectric gratings on the surface of the active layer are studied numerically. Their respective advantages are combined to achieve the complementary absorption enhancement.

Dual-Cavity Resonance for Broadband and Wide angle Absorption Enhancement in Thin Film Solar Cells

A grating structure based on cavity resonance was proposed to broadband light absorption enhancement in a-Si thin film solar cells. Dual-cavity resonance is excited for better light harvesting especially in long wavelength range.