• 한국태양에너지학회:학술대회논문집
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• 2011.11a
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• pp.34-39
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• 2011

Screen printing method is a common way to fabricate the crystalline silicon solar cell with low-cost and high-efficiency. The screen printing metallization use silver paste and aluminum paste for front and rear contact, respectively. Especially the rear contact between aluminum and silicon is important to form the back surface filed (Al-BSF) after firing process. BSF plays an important role to reduces the surface recombination due to $p^+$ doping of back surface. However, Al electrode on back surface leads to bow occurring by differences in coefficient of thermal expansion of the aluminum and silicon. In this paper, we studied the properties of mono crystalline silicon solar cell for rear electrode with aluminum and aluminum-boron in order to characterize bow and BSF of each paste. The 156*156 $m^2$ p-type silicon wafers with $200{\mu}m$ thickness and 0.5-3 ${\Omega}\;cm$ resistivity were used after texturing, diffusion, and antireflection coating. The characteristics of solar cells was obtained by measuring vernier callipers, scanning electron microscope and light current-voltage. Solar cells with aluminum paste on the back surface were achieved with $V_{OC}$ = 0.618V, JSC = 35.49$mA/cm^2$, FF(Fill factor) = 78%, Efficiency = 17.13%.

• Journal of the Korean Vacuum Society
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• v.20 no.3
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• pp.189-194
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• 2011

Si-cell was prepared with various types owing to the etching times textured by the KOH etching solution. The pn junction for solar cell was prepared on p-type Si wafer by the furnace using the $POCl_3$ and oxygen mixed precursor, and the metalization was done using by the Al back electrode and Ag front electrode. Textured Si surface was etched by the pyramid formation. The efficiency and the fill factor was increased in the Si-cell with a large size of pyramids, because of the series resistances decrease depending on the increasing of the photon absorbance. Increasing of the absorbance occurred the induction of the short current and open voltage, and then the efficiency was increased.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.112.1-112.1
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• 2011

The back contact solar cell (BCSC) has several advantages compared to the conventional solar cell since it can reduce grid shadowing loss and contact resistance between the electrode and the silicon substrate. This paper presents the effect of the surface texturing of the silicon BCSC by varying the texturing depth or the texturing gap in the commercially available simulation software, ATHENA and ATLAS of the company SILVACO. The texturing depth was varied from $5{\mu}m$ to $150{\mu}m$ and the texturing gap was varied from $1{\mu}m$ to $100{\mu}m$ in the simulation. The resulting efficiency of the silicon BCSC was evaluated depending on the texturing condition. The quantum efficiency and the I-V curve of the designed silicon BCSC was also obtained for the analysis since they are closely related with the solar cell efficiency. Other parameters of the simulated silicon BCSC are as follows. The substrate was an n-type silicon, which was doped with phosphorous at $6{\times}10^{15}cm^{-3}$, and its thickness was $180{\mu}m$, a typical thickness of commercial solar cell substrate thickness. The back surface field (BSF) was $1{\times}10^{20}\;cm^{-3}$ and the doping concentration of a boron doped emitter was $8.5{\times}10^{19}\;cm^{-3}$. The pitch of the silicon BCSC was $1250{\mu}m$ and the anti-reflection coating (ARC) SiN thickness was $0.079{\mu}m$. It was assumed that the texturing was anisotropic etching of crystalline silicon, resulting in texturing angle of 54.7 degrees. The best efficiency was 25.6264% when texturing depth was $50{\mu}m$ with zero texturing gap in case of low texturing depth (< $100{\mu}m$).

• Composites Research
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• v.24 no.6
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• pp.56-63
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• 2011

The objective of this study is to investigate appropriate bonding methods of solar cells in order to apply solar cells, which have been receiving particular attention as a renewable energy due to fossil energy depletion and environment issues, to composite structures. Back-contact solar cells with approximately 24.2% energy conversion efficiency were used in this study. Since silicon-based solar cells are mechanically fragile, the secondary-bonding methods using adhesive were examined in this study. The experiment was conducted with three kinds of bonding materials such as EVA film, Resin film and elastic adhesive. The performance of solar cells for three types of adhesives under mechanical loading on test specimens is conducted. In addition, the measuring equipment was designed to evaluate the performance of the solar cells under mechanical loading in real time and the fracture characteristics depending on bonding materials were evaluated. The reason decreasing solar cells efficiency were analyzed and considered by Fractography. The results show that the solar cell performance is largely affected by bonding techniques. Moreover, the bonding method using elastic adhesive shows best solar cell efficiency.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.91.1-91.1
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• 2010

There are some methods for increasing efficiency of crystalline silicon solar cells. Among them, It is important to reduce the recombination loss of surface for high efficiency. In order to reduce recombination loss is a way to use the BSF(Back Surface Field). The BSF on the back of the p-type wafer forms a p+layer. so, it is prevented to act electrons of the p-area for the rear recombination. As a result, the leakage current is reduced and the rear-contact has a good Ohmic contact. therefore, open-circuit-voltage and Fill factor(FF) of solar cells are increased. This paper investigates the formation of rear contact process comparing Aluminum-paste(Al-paste) with Aluminum-Metal(99.9%). It is shown that the Aluminum-Metal provides high conductivity and low contact resistance of $21.35m{\Omega}cm$ using the Vacuum evaporation process but, it is difficult to apply the standard industrial process because high Vacuum is needed and it costs a tremendous amount more than Al-paste. On the other hand, using the Al-paste process by screen printing is simple for formation of metal contact and it is possible to produce the standard industrial process. however, it is lower than Aluminum-Metal(99.9) of conductivity because of including mass glass frit. In this study, contact resistances were measured by 4-point prove. each of contact resistances is $21.35m{\Omega}cm$ of Aluminum-Metal and $0.69m{\Omega}cm$ of Al-paste. and then rear contact have been analyzed by Scanning Electron Microscopy(SEM).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.245-245
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• 2010

This paper and the rear passivation experiment was local back surface field Nd:$YVO_4$ green laser and the experiment was used performed to screen printing. Laser power 100%, with a fixed frequency for 60kHz Current of 29A and 30A were tested in two conditions. The point contact distances of 0.2mm, 0.4mm, 0.6mm, 0.8mm and 29A and 30A current conditions, it was found that is suitable for 0.4mm.

• Korean Journal of Materials Research
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• v.25 no.7
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• pp.336-340
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• 2015

For rear metallization with Al paste, Al back contacts require good passivation, high reflectance, and a processing temperature window compatible with the front metal. In this paper, the effect of the firing ambient during the metallization process on the formation of Al rear metal was investigated. We chose three different gases as ambient gases during the firing process. Using SEM, we observed the formation of a back surface field in $N_2$, $O_2$, and Air ambients. To determine the effect of the ambient on Voc, the suns-Voc tool was used. In this study, we described the mechanism of burn-out of organic materials in Al paste during the firing process. The oxygen ambient plays an important role in the burn-out process. We calculated the efficiency with obtained the back surface recombination velocities using PC1D simulation. It was found that the presence of oxygen during the firing process influenced the uniform back surface field because the organic materials in the Al paste were efficiently burned out during heating. The optimized temperature with oxygen flow shows an absolute efficiency of 19.1% at PC1D simulation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.7
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• pp.571-574
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• 2010

Surface recombination loss should be reduced for high efficiency of solar cells. To reduce this loss, the BSF (back surface field) is used. The BSF on the back of the p-type wafer forms a p+layer, which prevents the activity of electrons of the p-area for the rear recombination. As a result, the leakage current is reduced and the rear-contact has a good Ohmic contact. Therefore, the open-circuit-voltage (Voc) and fill factor (FF) of solar cells are increased. This paper investigates the formation of the rear contact process by comparing aluminum-paste (Al-paste) with pure aluminum-metal(99.9%). Under the vacuum evaporation process, pure aluminum-metal(99.9%) provides high conductivity and low contact resistance of $4.2\;m{\Omega}cm$, but It is difficult to apply the standard industrial process to it because high vacuum is needed, and it's more expensive than the commercial equipment. On the other hand, using the Al-paste process by screen printing is simple for the formation of metal contact, and it is possible to produce the standard industrial process. However, Al-paste used in screen printing is lower than the conductivity of pure aluminum-metal(99.9) because of its mass glass frit. In this study, contact resistances were measured by a 4-point probe. The contact resistance of pure aluminum-metal was $4.2\;m{\Omega}cm$ and that of Al-paste was $35.69\;m{\Omega}cm$. Then the rear contact was analyzed by scanning electron microscope (SEM).