Light Trapping Enhancement in a Thin Film with 2D Conformal Periodic Hexagonal Arrays

Abstract

Applying a periodic light trapping array is an effective method to improve the optical properties in thin-film solar cells. In this work, we experimentally and theoretically investigate the light trapping properties of two-dimensional periodic hexagonal arrays in the framework of a conformal amorphous silicon film. Compared with the planar reference, the double-sided conformal periodic structures with all feature periodicities of sub-wavelength (300 nm), mid-wavelength (640 nm), and infrared wavelength (2300 nm) show significant broadband absorption enhancements under wide angles. The films with an optimum periodicity of 300 nm exhibit outstanding antireflection and excellent trade-off between light scattering performance and parasitic absorption loss. The average absorption of the optimum structure with a thickness of 160 nm is 64.8 %, which is much larger than the planar counterpart of 38.5 %. The methodology applied in this work can be generalized to rational design of other types of high-performance thin-film photovoltaic devices based on a broad range of materials.Electronic supplementary materialThe online version of this article (doi:10.1186/s11671-015-0988-y) contains supplementary material, which is available to authorized users.

Numerical Study of the Wide‐angle Polarization‐Independent Ultra‐Broadband Efficient Selective Solar Absorber in the Entire Solar Spectrum

“…Finally, the calculated results show that total photothermal conversion efficiency for the metamaterial solar absorber can reach 91.53%, which is very close to the photothermal conversion efficiency (95.6%) of the ideal cut‐off solar absorber. The result shows greatly improvement of photothermal conversion efficiency compare to previously reported solar absorbers …”

“…With the increase of the incident angle, the absorption efficiency decrease slightly at the wavelength beyond 1000 nm, whereas the absorption efficiency is enhanced at the UV region with increasing the incident angle. Note that, even with a 60 degrees angle of incidence, the solar absorber can still maintain a high absorption above 94% at the range of 270–1240 nm and a low absorption below 20% at the wavelength beyond 2050 nm, which shows an excellent absorption performance better than most of previously reported solar absorbers at the normal incidence . As shown in Figure b, the absorption spectra with different incident angles at TE polarization are calculated and depicted.…”

“…For example, Li proposed and demonstrated a broadband absorber based on a symmetrical nanostructure consisting of tri‐layer Cr/SiO 2 /Cr uniform films on Si substrate, which realize a near‐perfect absorption with polarization‐independence from 450 to 800 nm . However, the high absorption can only be realized in visible range, causing a low overall efficiency in the entire solar spectrum, and the same problem also can be found in many reported solar absorbers . Liang proposed and numerically investigated a metamaterial‐based nanopyramid array with 17 metal/dielectric pairs, which shows an absorption exceeding 90% in the range of 200–2900 nm .…”

ZnO/a-Si distributed Bragg reflectors for light trapping in thin film solar cells from visible to infrared range

“…One of the key reasons for the low conversion efficiency of thin-film solar cells is the weak absorption in the wavelength range of long-wave visible to near-infrared (from 750 to 1500 nm). Intensive investigation has been made to enhance the absorption of a-Si in the this range [2,13,14]. However, most of the methods are to use the expensive noble metal nano-particles with complex techniques [14] for light trapping in infrared range, which are not suitable for industrial products with low cost.…”

“…Intensive investigation has been made to enhance the absorption of a-Si in the this range [2,13,14]. However, most of the methods are to use the expensive noble metal nano-particles with complex techniques [14] for light trapping in infrared range, which are not suitable for industrial products with low cost. Besides, few DBRs with a broad stopband spanning a wide spectrum from near-infrared to visible have been developed to harvest this spectrum for thin-film solar cells.…”