Flattened light-scattering substrate in thin film silicon solar cells for improved infrared response

Sai, Hitoshi; Kanamori, Yoshiaki; Kondo, Michio

doi:10.1063/1.3565249

Cited by 76 publications

(55 citation statements)

References 13 publications

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“…However, the large band gap of silicon solid restricts its applications in making optoelectronic devices for utilizing infrared (IR) light [1][2][3][4][5][6]. If its wavelength is longer than 1.1 μm, i.e., its photon energy is less than the silicon band gap energy (1.1 eV), the light cannot be absorbed as it passes through silicon solid because the photon energy is not large enough to excite an electron to the conduction band from the valence band of the silicon solid.…”

Section: Introductionmentioning

confidence: 99%

Femtosecond laser irradiation-induced infrared absorption on silicon surfaces

Zhu

2015

International Journal of Smart and Nano Materials

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The near-infrared (NIR) absorption below band gap energy of crystalline silicon is significantly increased after the silicon is irradiated with femtosecond laser pulses at a simple experimental condition. The absorption increase in the NIR range primarily depends on the femtosecond laser pulse energy, pulse number, and pulse duration. The Raman spectroscopy analysis shows that after the laser irradiation, the silicon surface consists of silicon nanostructure and amorphous silicon. The femtosecond laser irradiation leads to the formation of a composite of nanocrystalline, amorphous, and the crystal silicon substrate surface with microstructures. The composite has an optical absorption enhancement at visible wavelengths as well as at NIR wavelength. The composite may be useful for an NIR detector, for example, for gas sensing because of its large surface area.

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Section: Introductionmentioning

confidence: 99%

Femtosecond laser irradiation-induced infrared absorption on silicon surfaces

Zhu

2015

International Journal of Smart and Nano Materials

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“…Although simulation results show a significant improvement of optical absorption compared with the flat one, the current experimental results were not so satisfactory [11,23]. As a matter of fact, the steep valleys of the gratings would inevitably result in micro voids within the absorption layers and then cause deterioration of the device performance [32]. Some other groups suggest depositing 1D-PC on a textured substrate (random [16] or periodic grating [23]).…”

Section: Tcpc Brs Formed By 1d-pc and Textured Znomentioning

confidence: 89%

“…However, experimental results were unsatisfactory. One probable reason is that the steep valleys of gratings inevitably lead to undesirable metastable defects at microvoids within the absorption layers, which then deteriorate the material properties and device performances [32]. On the other hand, the moderately random textures of post-chemically etched AZO films result in less microvoids and then less undesirable metastable defects, which are favorable for high-quality thin silicon layers and high efficiency solar cells [29].…”

Section: Introductionmentioning

confidence: 99%

Photonic Structures for Light Trapping in Thin Film Silicon Solar Cells: Design and Experiment

et al. 2017

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Abstract:One of the foremost challenges in designing thin-film silicon solar cells (TFSC) is devising efficient light-trapping schemes due to the short optical path length imposed by the thin absorber thickness. The strategy relies on a combination of a high-performance back reflector and an optimized texture surface, which are commonly used to reflect and scatter light effectively within the absorption layer, respectively. In this paper, highly promising light-trapping structures based on a photonic crystal (PC) for TFSCs were investigated via simulation and experiment. Firstly, a highly-reflective one-dimensional photonic crystal (1D-PC) was designed and fabricated. Then, two types of 1D-PC-based back reflectors (BRs) were proposed: Flat 1D-PC with random-textured aluminum-doped zinc oxide (AZO) or random-textured 1D-PC with AZO. These two newly-designed BRs demonstrated not only high reflectivity and sufficient conductivity, but also a strong light scattering property, which made them efficient candidates as the electrical contact and back reflector since the intrinsic losses due to the surface plasmon modes of the rough metal BRs can be avoided. Secondly, conical two-dimensional photonic crystal (2D-PC)-based BRs were investigated and optimized for amorphous a-SiGe:H solar cells. The maximal absorption value can be obtained with an aspect ratio of 1/2 and a period of 0.75 µm. To improve the full-spectral optical properties of solar cells, a periodically-modulated PC back reflector was proposed and experimentally demonstrated in the a-SiGe:H solar cell. This periodically-modulated PC back reflector, also called the quasi-crystal structure (QCS), consists of a large periodic conical PC and a randomly-textured Ag layer with a feature size of 500-1000 nm. The large periodic conical PC enables conformal growth of the layer, while the small feature size of Ag can further enhance the light scattering. In summary, a comprehensive study of the design, simulation and fabrication of 1D-PC-and 2D-PC-based back reflectors for TFSCs was carried out. Total absorption and device performance enhancement were achieved with the novel PC light-trapping systems because of their high reflectivity or high scattering property. Further research is necessary to illuminate the optimal structure design of PC-based back reflectors and high solar cell efficiency.

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“…These substrates were already investigated by Sai et al [9] and by our laboratory [10]. The high V oc (520 mV) and the large efficiency increase (20%) compared to a textured reference cell demonstrate the high potential of this polished substrate for high-efficiency solar cells.…”

Section: Introductionmentioning

confidence: 99%

Electrically flat/optically rough substrates for efficiencies above 10% in n-i-p thin-film silicon solar cells

et al. 2012

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Substrates with extremely low roughness to allow the growth of good-quality silicon material but that nevertheless present high light trapping properties are presented. In a first application, silver reflectors are used in single and tandem-junction amorphous silicon (a-Si:H) solar cells. High initial (stable) efficiencies of 10.4 % (8.1 %) for single-junction a-Si:H cells on glass and 11.1 % (9.2 %) for tandem-junction a-Si:H/a-Si:H cells on plastic are obtained. A second application better suited to multi-junction solar cells based on microcrystalline silicon (μc-Si:H) solar cells is presented: the substrate consists of rough zinc oxide (ZnO) grown on a flat silver reflector which is covered with a-Si:H; polishing of this structure yields an a-Si:H/ZnO interface that provides high light scattering even though the cell is deposited on a flat interface. We present results of ~ 4-μm-thick μc-Si:H solar cells prepared on such substrates with high open-circuit voltages of 520 mV. A large relative efficiency gain of 20% is observed compared to a co-deposited cell grown directly on an optimized textured substrate.

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Flattened light-scattering substrate in thin film silicon solar cells for improved infrared response

Cited by 76 publications

References 13 publications

Femtosecond laser irradiation-induced infrared absorption on silicon surfaces

Femtosecond laser irradiation-induced infrared absorption on silicon surfaces

Photonic Structures for Light Trapping in Thin Film Silicon Solar Cells: Design and Experiment

Electrically flat/optically rough substrates for efficiencies above 10% in n-i-p thin-film silicon solar cells

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