Efficiency enhancement in Si solar cells by textured photonic crystal back reflector

Abstract

An efficient light-trapping scheme is developed for solar cells that can enhance the optical path length by several orders of magnitude using a textured photonic crystal as a backside reflector. It comprises a reflection grating etched on the backside of the substrate and a one-dimensional photonic crystal deposited on the grating. Top-contacted crystalline Si solar cells integrated with the textured photonic crystal back reflector were designed and fabricated. External quantum efficiency was significantly improved between the wavelengths of 1000 and 1200nm (enhancement up to 135 times), and the overall power conversion efficiency was considerably increased.

Nanostructures for photon management in solar cells

“…In addition to reflectivity generated by a photonic band-gap, scattering or coupling to waveguide modes may be desired from photonic crystal reflectors. Zeng and colleagues [ 93 ] fabricated a crystalline silicon solar cell on top of a 675 μ m-thick silicon wafer; one-dimensional gratings with a 1.1 μ m period were patterned on the backside through projection photolithography and etching, and DBRs were deposited by plasma-enhanced chemical vapour deposition. The DBR was designed to have strong reflectivity in the wavelength range from 800 to 1100 nm, while the grating was designed to diffract incident light at these wavelengths well beyond the critical angle for total internal reflection in silicon.…”

Quantum dot micropillar cavities with quality factors exceeding 250,000

“…They are widely utilized in state-of-the-art vertically emitting microcavity lasers [1], optical filters, spin-photon interfaces [2] and they might also be useful for increasing the efficiency of solar cells [3,4]. However, the very high quality factors that can be provided by DBR-based microcavity structures also explains their important role in fundamental semiconductor optics, in particular in the research field of lightmatter interaction in semiconductors [5].…”

Modulated photonic-crystal structures as broadband back reflectors in thin-film solar cells

“…[1][2][3][4][5][6][7] While two-or three-dimensional PCs exhibit a high potential for efficient light scattering, 1,5 one-dimensional ͑1D͒ PCs can be used as distributed Bragg reflectors with high optical reflectance ͑close to 100%͒. 2,7 A regular 1D PC is a periodiclike multilayer structure consisting of two alternating layers each with a different refractive index ͑n 1 , n 2 ͒ and thickness ͓d 1 where m is the number of alternating-layer pairs ͑periods͒ in the PC structure and n 1 and n 2 are their refractive indices. 1 The high reflectance that can be achieved if the number of periods and the ratio between n 1 and n 2 are sufficiently large refers to a limited wavelength interval around 0 .…”