• Korean Journal of Materials Research
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• v.22 no.9
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• pp.450-453
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• 2012

In crystalline solar cells, the substrate itself constitutes a large portion of the fabrication cost as it is derived from semiconductor ingots grown in costly high temperature processes. Thinner wafer substrates allow some cost saving as more wafers can be sliced from a given ingot, although technological limitations in slicing or sawing of wafers off an ingot, as well as the physical strength of the sliced wafers, put a lower limit on the substrate thickness. Complementary to these economical and techno-physical points of view, a device operation point of view of the substrate thickness would be useful. With this in mind, BC-BJ Si and GaAs solar cells are compared one to one by means of the Medici device simulation, with a particular emphasis on the substrate thickness. Under ideal conditions of 0.6 ${\mu}m$ photons entering the 10 ${\mu}m$-wide BC-BJ solar cells at the normal incident angle (${\theta}=90^{\circ}$), GaAs is about 2.3 times more efficient than Si in terms of peak cell power output: 42.3 $mW{\cdot}cm^{-2}$ vs. 18.2 $mW{\cdot}cm^{-2}$. This strong performance of GaAs, though only under ideal conditions, gives a strong indication that this material could stand competitively against Si, despite its known high material and process costs. Within the limitation of the minority carrier recombination lifetime value of $5{\times}10^{-5}$ sec used in the device simulation, the solar cell power is known to be only weakly dependent on the substrate thickness, particularly under about 100 ${\mu}m$, for both Si and GaAs. Though the optimum substrate thickness is about 100 ${\mu}m$ or less, the reduction in the power output is less than 10% from the peak values even when the substrate thickness is increased to 190 ${\mu}m$. Thus, for crystalline Si and GaAs with a relatively long recombination lifetime, extra efforts to be spent on thinning the substrate should be weighed against the expected actual gain in the solar cell output power.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.10
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• pp.844-849
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• 2011

Two kind of Ag-pastes were prepared for integrating the bulk Si solar cell. One is the Ag-paste with Pb-based glass frit and the other is that with Bi-based glass frit. The pastes were the mixture of 84 wt% Ag, 2 wt% glass frit, 11 wt% solvent of buthyl cabitol acetate, and 2 wt% additives. After fabricating the Ag-pastes, they was coated on a $SiN_x$/n+/p- stacks of a commercial mono-Si solar cell. The solar cell efficiency was 17.6% in the case of the Pb-based Ag-paste. However that was 16.2% in the solar cell integrated with the Bi-based Ag-paste. The lower performance in Bi-based Ag-paste was caused by the higher series resistance and the lower shunt resistance in comparison with the Pb-based Ag-paste.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.2060-2060
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• 2011

This paper was investigated the frequency property for optimal operating conditions of mono-crystalline Si solar cell. An internal impedance of mono-crystalline Si solar cell was influenced frequency. An optimal operating conditions of solar cell was under about 10[kHz].

• Journal of the Korean Society of Safety
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• v.18 no.3
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• pp.64-68
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• 2003

ITO_{(n)}/Si_{(p)}$ solar cell is fabricated by vaccum deposition method under the resistance heating with substrate temperature kept about 200[$^{\circ}C$] and than their properties are investigated. The maximum output of fabricated solar cell is obtained when the composition of the thin film is consisted of indium oxide 91[mole %] and tin oxide 9(mole %). The solar cell electrical charateristics can be improved by annealing but are deteriorated at temperature above 600[$^{\circ}C$] for longer than 15[min].

• 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.

• 한국신재생에너지학회:학술대회논문집
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• 2008.10a
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• pp.124-127
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• 2008

Dye-sensitized solar cells (DSCs) have been proposed as a substitute for overcoming the limitation of Si solar cells because DSC has the various applications using advantages of DSC such as low cost, transparency and flexibility. Although some people point out low efficiency of DSC as the important problem at present, general views say that actually cumulative power is not insufficient as compared with Si solar cell. Therefore, we analyzed the characteristics of both cells according to the change of incident angle in this study. The insensibility about the incident angle has more developable time. Finally, DSC is able to fill a shortage of power caused from low efficiency of DSC for same time by developing during impossible time to develop in Si solar cell. As a result, DSC has 75% and 210% cumulative power of Si solar cell in summer and winter under the standard sunshine duration.

• Journal of the Optical Society of Korea
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• v.19 no.2
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• pp.199-205
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• 2015

We investigated the effects of the thickness and doping concentration in p- and n-type poly-Si layers on the performance of a solar cell based on a carbon fiber in order to improve the energy conversion efficiency of the cell. The short-circuit current density and open-circuit voltage of the carbon fiber-based solar cell were significantly influenced by the thickness and doping concentration in the p- and n-type poly-Si layers. The solar cell efficiency was successfully enhanced to ~10.5%.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.207-207
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• 2012

Si quantum dot (QD) imbedded in a $SiO_2$ matrix is a promising material for the next generation optoelectronic devices, such as solar cells and light emission diodes (LEDs). However, low conductivity of the Si quantum dot layer is a great hindrance for the performance of the Si QD-based optoelectronic devices. The effective doping of the Si QDs by semiconducting elements is one of the most important factors for the improvement of conductivity. High dielectric constant of the matrix material $SiO_2$ is an additional source of the low conductivity. Active doping of B was observed in nanometer silicon layers confined in $SiO_2$ layers by secondary ion mass spectrometry (SIMS) depth profiling analysis and confirmed by Hall effect measurements. The uniformly distributed boron atoms in the B-doped silicon layers of $[SiO_2(8nm)/B-doped\;Si(10nm)]_5$ films turned out to be segregated into the $Si/SiO_2$ interfaces and the Si bulk, forming a distinct bimodal distribution by annealing at high temperature. B atoms in the Si layers were found to preferentially substitute inactive three-fold Si atoms in the grain boundaries and then substitute the four-fold Si atoms to achieve electrically active doping. As a result, active doping of B is initiated at high doping concentrations above $1.1{\times}10^{20}atoms/cm^3$ and high active doping of $3{\times}10^{20}atoms/cm^3$ could be achieved. The active doping in ultra-thin Si layers were implemented to silicon quantum dots (QDs) to realize a Si QD solar cell. A high energy conversion efficiency of 13.4% was realized from a p-type Si QD solar cell with B concentration of $4{\times}1^{20}atoms/cm^3$. We will present the diffusion behaviors of the various dopants in silicon nanostructures and the performance of the Si quantum dot solar cell with the optimized structures.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.5
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• pp.30-35
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• 2013

In order to increase cell efficiency in crystalline silicon solar cell, reduction of light reflection is one of the essential problem. Until now silicon wafer was textured by wet etching process which has random patterns along crystal orientation. In this study, high aspect ratio patterns are manufactured by nano imprint process and reflectance could be minimized under 1%. After that, screen printed solar cell was fabricated on the textured wafer and I-V characteristics was measured by solar simulator. Consequently cell efficiency of solar cell fabricated using the wafer textured by nano imprint process increased 1.15% than reference solar cell textured by wet etching. Internal quantum efficiency was increased in the range of IR wave length but decreased in the UV wavelength. In spite of improved result, optimization between nano imprinted pattern and solar cell process should be followed.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.287.2-287.2
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• 2016

Silicon has considerably good characteristics on electron, hole mobility and its price. With 2-D sinlge-layer Graphene/n-Si heterojunction solar cell shows that in one sun condition exhibit power conversion efficiency(PCE) of 10.1%. This photovoltaic effect was achieved by applying gate voltage to the Schottky junction of the heterostructure solar cell. Energy band diagram shows that Schottky barrier between Si and graphene can be adjust by the external electric field. because of the fermi level of the graphene can be changed by external gate voltage, we can control the Schottkky barrier of the heterostructure solar cell. The ratio between generated power of solar cell and consumption electrical power is remarkable. Since we use the graphene as the top gate electrode, most of the sun light can penetrate into the active area.