• Title/Summary/Keyword: a-Si thin film solar cell

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Thin Film Si-Ge/c-Si Tandem Junction Solar Cells with Optimum Upper Sub- Cell Structure

  • Park, Jinjoo
    • Current Photovoltaic Research
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    • v.8 no.3
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    • pp.94-101
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    • 2020
  • This study was trying to focus on achieving high efficiency of multi junction solar cell with thin film silicon solar cells. The proposed thin film Si-Ge/c-Si tandem junction solar cell concept with a combination of low-cost thin-film silicon solar cell technology and high-efficiency c-Si cells in a monolithically stacked configuration. The tandem junction solar cells using amorphous silicon germanium (a-SiGe:H) as an absorption layer of upper sub-cell were simulated through ASA (Advanced Semiconductor Analysis) simulator for acquiring the optimum structure. Graded Ge composition - effect of Eg profiling and inserted buffer layer between absorption layer and doped layer showed the improved current density (Jsc) and conversion efficiency (η). 13.11% conversion efficiency of the tandem junction solar cell was observed, which is a result of showing the possibility of thin film Si-Ge/c-Si tandem junction solar cell.

Metal-assisted grown Si films and semiconducting nanowires for solar cells

  • Kim, Jun-Dong
    • Proceedings of the Materials Research Society of Korea Conference
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    • 2010.05a
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    • pp.13-13
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    • 2010
  • The solar energy conversion will take 10 % global energy need by 2033. A thin film type solar cell has been considered as one of the promising candidates for a large area applicable solar cell fabrication at a low cost. The metal-assisted growth of microcrystalline Si (mc-Si) films has been reported for a quality Si film synthesis at a low temperature. It discusses the spontaneous growth of a Si film above a metal-layer for a thin film solar cell. Quite recently, a substantial demand of nanomaterials has been addressed for cost-effective solar cells. The nanostructure provides a large photoactive surface at a fixed volume, which is an advantage in the effective use of solar power. But the promising of nanostructure active solar cell has not been much fulfilled due mainly to the difficulty in architecture of nanostructures. We present here the Si nanowire (SiNW)-embedded Schottky solar cell. Multiple SiNWs were connected to two different metals to form a Schottky or an ohmic contact according to the metal work function values. It discusses the scheme of rectifying contact between metals and SiNWs and the SiNW-embedded Schottky solar cell performances.

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Performance Improvement of Flexible Thin Film Si Solar Cells using Graphite Substrate (그라파이트 기판을 이용한 유연 박막 실리콘 태양전지 특성 향상)

  • Lim, Gyeong-yeol;Cho, Jun-sik;Chang, Hyo Sik
    • Korean Journal of Materials Research
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    • v.29 no.5
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    • pp.317-321
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    • 2019
  • We investigated the characteristics of nano crystalline silicon(nc-Si) thin-film solar cells on graphite substrates. Amorphous silicon(a-Si) thin-film solar cells on graphite plates show low conversion efficiency due to high surface roughness, and many recombination by dangling bonds. In previous studies, we deposited barrier films by plasma enhanced chemical vapor deposition(PECVD) on graphite plate to reduce surface roughness and achieved ~7.8 % cell efficiency. In this study, we fabricated nc-Si thin film solar cell on graphite in order to increase the efficiency of solar cells. We achieved 8.45 % efficiency on graphite plate and applied this to nc-Si on graphite sheet for flexible solar cell applications. The characterization of the cell is performed with external quantum efficiency(EQE) and current density-voltage measurements(J-V). As a result, we obtain ~8.42 % cell efficiency in a flexible solar cell fabricated on a graphite sheet, which performance is similar to that of cells fabricated on graphite plates.

New Generation Multijunction Solar Cells for Achieving High Efficiencies

  • Lee, Sunhwa;Park, Jinjoo;Kim, Youngkuk;Kim, Sangho;Iftiquar, S.M.;Yi, Junsin
    • Current Photovoltaic Research
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    • v.6 no.2
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    • pp.31-38
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    • 2018
  • Multijunction solar cells present a practical solution towards a better photovoltaic conversion for a wider spectral range. In this review, we compare different types of multi-ijunction solar cell. First, we introduce thin film multijunction solar cell include to the thin film silicon, III-V material and chalcopyrite material. Until now the maximum reported power conversion efficiencies (PCE) of solar cells having different component sub-cells are 14.0% (thin film silicon), 46% (III-V material), 4.4% (chalcopyrite material) respectively. We then discuss the development of multijunction solar cell in which c-Si is used as bottom sub-cell while III-V material, thin film silicon, chalcopyrite material or perovskite material is used as top sub-cells.

The Effect of Barrier Layer on Thin-film Silicon Solar Cell Using Graphite Substrates (탄소 기판을 이용한 박막 실리콘 태양전지의 배리어 층 효과)

  • Cho, Young Joon;Lee, Dong Won;Cho, Jun Sik;Chang, Hyo Sik
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.29 no.8
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    • pp.505-509
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    • 2016
  • We have investigated the characteristics of amorphous silicon (a-Si) thin-film solar cell by inserting barrier layer. The conversion efficiency of a-Si thin-film solar cells on graphite substrate shows nearly zero because of the surface roughness of the graphite substrate. To enhance the performance of solar cells, the surface morphology of the back side were modified by changing the barrier layer on graphite. The surface roughness of graphite substrate with the barrier layer grown by plasma enhanced chemical vapor deposition (PECVD) reduced from ~2 um to ~75 nm. In this study, the combination of the barrier layer on graphite substrate is important to increase solar cell efficiency. We achieved ~ 7.8% cell efficiency for an a-Si thin-film solar cell on graphite substrate with SiNx/SiOx stack barrier layer.

[ $a-Si:H/{\mu}c-Si:H$ ] thin-film tandem solar cells (비정질/마이크로 탠덤 구조형 실리콘 박막 태양전지)

  • Lee, Jeong-Chul;Song, Jin-Soo;Yoon, Kyung-Hoon
    • 한국신재생에너지학회:학술대회논문집
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    • 2006.06a
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    • pp.228-231
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    • 2006
  • This paper briefly introduces silicon based thin film solar cells: amorphous (a-Si:H), microcrystalline ${\mu}c-Si:H$ single junction and $a-Si:H/{\mu}c-Si:H$ tandem solar cells. The major difference of a-Si:H and ${\mu}c-Si:H$ cells comes from electro-optical properties of intrinsic Si-films (active layer) that absorb incident photon and generate electron-hole pairs. The a-Si:H film has energy band-gap (Eg) of 1.7-1.8eV and solar cells incorporating this wide Eg a-Si:H material as active layer commonly give high voltage and low current, when illuminated, compared to ${\mu}c-Si:H$ solar cells that employ low Eg (1.1eV) material. This Eg difference of two materials make possible tandem configuration in order to effectively use incident photon energy. The $a-Si:H/{\mu}c-Si:H$ tandem solar cells, therefore, have a great potential for low cost photovoltaic device by its various advantages such as low material cost by thin-film structure on low cost substrate instead of expensive c-Si wafer and high conversion efficiency by tandem structure. In this paper, the structure, process and operation properties of Si-based thin-film solar cells are discussed.

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Plasmonic Enhanced Light Absorption by Silver Nanoparticles Formed on Both Front and Rear Surface of Polycrystalline Silicon Thin Film Solar Cells

  • Park, Jongsung;Park, Nochang;Varlamov, Sergey
    • Proceedings of the Korean Vacuum Society Conference
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    • 2014.02a
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    • pp.493-493
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    • 2014
  • The manufacturing cost of thin-film photovoltics can potentially be lowered by minimizing the amount of a semiconductor material used to fabricate devices. Thin-film solar cells are typically only a few micrometers thick, whereas crystalline silicon (c-Si) wafer solar cells are $180{\sim}300\mu}m$ thick. As such, thin-film layers do not fully absorb incident light and their energy conversion efficiency is lower compared with that of c-Si wafer solar cells. Therefore, effective light trapping is required to realize commercially viable thin-film cells, particularly for indirect-band-gap semiconductors such as c-Si. An emerging method for light trapping in thin film solar cells is the use of metallic nanostructures that support surface plasmons. Plasmon-enhanced light absorption is shown to increase the cell photocurrent in many types of solar cells, specifically, in c-Si thin-film solar cells and in poly-Si thin film solar cell. By proper engineering of these structures, light can be concentrated and coupled into a thin semiconductor layer to increase light absorption. In many cases, silver (Ag) nanoparticles (NP) are formed either on the front surface or on the rear surface on the cells. In case of poly-Si thin film solar cells, Ag NPs are formed on the rear surface of the cells due to longer wavelengths are not perfectly absorbed in the active layer on the first path. In our cells, shorter wavelengths typically 300~500 nm are also not effectively absorbed. For this reason, a new concept of plasmonic nanostructure which is NPs formed both the front - and the rear - surface is worth testing. In this simulation Al NPs were located onto glass because Al has much lower parasitic absorption than other metal NPs. In case of Ag NP, it features parasitic absorption in the optical frequency range. On the other hand, Al NP, which is non-resonant metal NP, is characterized with a higher density of conduction electrons, resulting in highly negative dielectric permittivity. It makes them more suitable for the forward scattering configuration. In addition to this, Ag NP is located on the rear surface of the cell. Ag NPs showed good performance enhancement when they are located on the rear surface of our cells. In this simulation, Al NPs are located on glass and Ag NP is located on the rear Si surface. The structure for the simulation is shown in figure 1. Figure 2 shows FDTD-simulated absorption graphs of the proposed and reference structures. In the simulation, the front of the cell has Al NPs with 70 nm radius and 12.5% coverage; and the rear of the cell has Ag NPs with 157 nm in radius and 41.5% coverage. Such a structure shows better light absorption in 300~550 nm than that of the reference cell without any NPs and the structure with Ag NP on rear only. Therefore, it can be expected that enhanced light absorption of the structure with Al NP on front at 300~550 nm can contribute to the photocurrent enhancement.

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A Study on the Residual Stress Analysis of a-Si Thin Film Solar Cell (a-Si 박막형 태양전지의 잔류응력 해석에 관한 연구)

  • Hur, Jang-Wook;Kim, Dong-Wook;Choi, Sung-Dae
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.12 no.2
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    • pp.14-19
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    • 2013
  • The size and distribution of residual stresses and the effect of the minimum mesh size were investigated by the a-Si thin film solar cell. Attributed to the difference in coefficient of thermal expansion of the a-Si and Ag concentrated residual stresses at the joint interface of dissimilar materials. The ${\sigma}y$ and ${\tau}xy$ didn't appear in the central part, but ${\sigma}x$ existed. However, ${\sigma}x$, ${\sigma}y$ and ${\tau}xy$ appeared in the edge part and concentrated residual stresses at the interface between a-Si and Ag. Minimum mesh size gets smaller, the concentration of ${\sigma}y$ was significantly and existence area was reduced. As a result, the failure of thin film solar cells during the cutting process can be explained by the residual stresses.

Evaluation of Solar Cell Properties of Poly-Si Thin Film Fabricated with Novel Process Conditions for Solid Phase Crystallization (고상 결정화법을 위한 새로운 공정조건으로 제작된 다결정 Si 박막의 태양전지 특성 평가)

  • Kweon, Soon-Yong;Jeong, Ji-Hyun;Tao, Yuguo;Varlamov, Sergey
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.24 no.9
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    • pp.766-772
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    • 2011
  • Amorphous Si (a-Si) thin films of $p^+/p^-/n^+$ were deposited on $Si_3N_4$/glass substrate by using a plasma enhanced chemical vapor deposition (PECVD) method. These films were annealed at various temperatures and for various times by using a rapid thermal process (RTP) equipment. This step was added before the main thermal treatment to make the nuclei in the a-Si thin film for reducing the process time of the crystallization. The main heat treatment for the crystallization was performed at the same condition of $600^{\circ}C$/18 h in conventional furnace. The open-circuit voltages ($V_{oc}$) were remained about 450 mV up to the nucleation condition of 16min in the nucleation RTP temperature of $680^{\circ}C$. It meat that the process time for the crystallization step could be reduced by adding the nucleation step without decreasing the electrical property of the thin film Si for the solar cell application.

Electrical characteristics of Sn $O_{2}$Si heterojunction solar cells depending on annealing temperature (열처리온도에 따른 $SnO_2$/Si 이종접합 태양전지의 전기적 특성)

  • 이재형;박용관
    • Electrical & Electronic Materials
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    • v.7 no.6
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    • pp.481-489
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    • 1994
  • The $SnO_2$/(n)Si solar cell was fabricated by electron beam evaporation method, and their properties were investigated. In proportion to increase of substrate and annealing temperature, the conductivity of $SnO_2$ thin film was increased, but its optical transmission decreases because of increasing optical absorption of free electrons in the thin film. $SnO_2$/Si Solar cell characteristics were improved by annealing, but the solar cells was deteriorated by heat treatment above 500[.deg. C]. The optimal outputs of $SnO_2$/Si solar cell through above investigations were $V_{\var}$:350[mV], $J_{sc}$ ;16.53[mA/c $m^{2}$], FF;0.41, .eta.=4.74[%]

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