• Korean Journal of Materials Research
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• v.22 no.8
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• pp.390-396
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• 2012

Ag pastes added to Bi-oxide frits have been applied to the electrode material of Si solar cells. It has been reported that frits induce contacts between the Ag electrodes and the Si wafer after firing. During firing, the control of interfaces among Ag, the glass layer, and Si is one of the key factors for improving cell performance. Specifically, the thermo-physical properties of frits considerably influence Ag-Si contact. Therefore, the thermal properties of frits should be carefully controlled to enhance the efficiency of cells. In this study, the interface structures among Ag electrodes, glass layers, and recrystallites on an $n^+$ emitter were carefully analyzed with the thermal properties of lead-free frits. First, a cross-section of the area between the Ag electrodes and the Si wafer was studied in order to understand the interface structures in light of the thermal properties of the frits. The depth and area of the pits formed in the Si wafer were quantitatively calculated with the thermal properties of frits. The area of the glass layers between the Ag electrodes and Si, and the distribution of recrystallites on the $n^+$ emitter, were measured from a macroscopic point of view with the characteristics of the frits. Our studies suggest that the thermophysical properties should be controlled for the optimal performance of Si solar cells; our studies also show why cell performance deteriorated due to the high viscosity of frits in Ag pastes.

• Current Photovoltaic Research
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• v.10 no.4
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• pp.95-100
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• 2022

Solar cell is a device that converts photon energy into electrical energy. Therefore, absorption of solar spectrum light is one of the most important characteristics to design the solar cell structures. Various methods have emerged to reduce optical losses, such as textured surfaces, back contact solar cells, anti-reflection layers. Here, the anti-reflection coating (ARC) layer is typically utilized whose refractive index value is between air (~1) and silicon (~4) such as SiN_x layer (~1.9). This research is to print a material called polydimethylsiloxane (PDMS) to form a double anti-reflection layer. Light with wavelength in the range of 0.3 to 1.2 micrometers does not share a wavelength with solar cells. It is confirmed that the refractive index of PDMS (~1.4) is an ARC layer which decreases the reflectance of light absorption region on typical p-type solar cells with SiN_x layer surface. Optimized PDMS printing with analyzing optical property for cell structure can be the effective way against outer effects by encapsulation.

• Solar Energy
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• v.6 no.1
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• pp.12-23
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• 1986

The PECVD $SiN_x:H$ films were made from the $SiH_4-N_2$ gas mixtures under such deposition conditions as 0.01 to 1.0 of $SiH_4/N_2$ volume ratio, 0.1 to $0.8W/cm^2$ of RF power, and 100 to $400^{\circ}C$ of substrate temperature. The deposition rate, refractive index, hydrogen concentration, N/Si composition, optical gap and electric conductivity were measured, and the thermal stability and the optimum deposition conditions were investigated for the application of these films to the solar cell materials.

• Current Photovoltaic Research
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• v.7 no.4
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• pp.130-133
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• 2019

The Ag crystallite formed during the formation of the front electrode forms a contact between the metal of the electrode and the emitter of the cell. Contact between the electrode and emitter plays an important role in collecting electrons generated by the solar cell. Therefore, Ag crystallite formation is an important factor. In order for solar cells to have good characteristics, it is important to understand the factors influencing the Ag crystallite formation. Factors affecting the formation of Ag crystallites include Si emitter, morphology, Si defect and firing temperature. The influence of surface morphology on Ag crystallite formation was confirmed throughout this study. In the case of fine texturing, the Ag crystallites were formed at the pointed parts. The finer the texturing, the sharper areas and more Ag crystallites were formed. This was confirmed by SEM image and FF calculation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.243-243
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• 2010

This paper two different etching, HF : HNO3 :DI and RIE were used for etching in multi-crystalline Silicon(Mc-Si) solar cell fabrication. The wafers etched in RIE texture showed low reflectance compared to the wafers etched in Acid soultion after SiNx deposition. In light current-voltage results, the cells etched in RIE texture exhibited higher short circuit current and open circuit voltage than those of the cells etched in acid solution. We have obtained 15.1% conversion efficiency in large area($156cm^2$) Multi-Si solar cells etched in RIE texture.

• Journal of the Korean institute of surface engineering
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• v.40 no.3
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• pp.138-143
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• 2007

The effects of texturing and anti-reflection coating on the reflection properties of multi-crystalline silicon solar cell have been investigated. The chemical solutions of alkaline and acidic etching solutions were used for texturing at the surface of multi-crystalline Si wafer. Experiments were performed with various temperature and time conditions in order to determine the optimized etching condition. Alkaline etching solution was found inadequate to the texturing of multi-crystalline Si due to its high reflectance of about 25%. The reflectance of Si wafer texturing with acidic etching solution showed a very low reflectance about 10%, which was attributed to the formation of homogeneous. Also, deposition of ITO anti-reflection coating reduced the reflectance of multi-crystalline si etched with acidic solution($HF+HNO_3$) to 2.6%.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.247.1-247.1
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• 2016

Low-cost, high efficiency solar cells are tremendous interests for the realization of a renewable and clean energy source. ZnTe based solar cells have a possibility of high efficiency with formation of an intermediated energy band structure by impurity doping. In this work, ZnO/ZnTe:Cr and ZnO/i-ZnTe structures were fabricated by pulsed laser deposition (PLD) technique. A pulsed (10 Hz) Nd:YAG laser operating at a wavelength of 266 nm was used to produce a plasma plume from an ablated a ZnTe target, whose density of laser energy was 10 J/cm2. The base pressure of the chamber was kept at approximately $4{\times}10-7Torr$. ZnTe:Cr and i-ZnTe thin films with thickness of 210 nm were grown on p-Si substrate, respectively, and then ZnO thin films with thickness of 150 nm were grown on ZnTe:Cr layer under oxygen partial pressure of 3 mTorr. Growth temperature of all the films was set to $250^{\circ}C$. For fabricating ZnO/i-ZnTe and ZnO/ZnTe:Cr solar cells, indium metal and Ti/Au grid patterns were deposited on back and front side of the solar cells by using thermal evaporator, respectively. From the fabricated ZnO/ZnTe:Cr and ZnO/i-ZnTe solar cell, dark currents were measured by using Keithley 2600. Solar cell parameters were obtained under Air Mass 1.5 Global solar simulator with an irradiation intensity of 100 mW/cm2, and then the photoelectric conversion efficiency values of ZnO/ZnTe:Cr and ZnO/i-ZnTe solar cells were measured at 1.5 % and 0.3 %, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.456-456
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• 2009

Boron doping on an n-type Si wafer is requisite process for IBC (Interdigitated Back Contact) solar cells. Fiber laser annealing is one of boron doping methods. For the boron doping, uniformly coated or deposited film is highly required. Plasma enhanced chemical vapor deposition (PECVD) method provides a uniform dopant film or layer which can facilitate doping. Because amorphous silicon layer absorption range for the wavelength of fiber laser does not match well for the direct annealing. In this study, to enhance thermal affection on the existing p-a-Si:H layer, a ${\mu}c$-Si:H intrinsic layer was deposited on the p-a-Si:H layer additionally by PECVD. To improve heat transfer rate to the amorphous silicon layer, and as heating both sides and protecting boron eliminating from the amorphous silicon layer. For p-a-Si:H layer with the ratio of $SiH_4$ : $B_2H_6$ : $H_2$ = 30 : 30 : 120, at $200^{\circ}C$, 50 W, 0.2 Torr for 30 minutes, and for ${\mu}c$-Si:H intrinsic layer, $SiH_4$ : $H_2$ = 10 : 300, at $200^{\circ}C$, 30 W, 0.5 Torr for 60 minutes, 2 cm $\times$ 2 cm size wafers were used. In consequence of comparing the results of lifetime measurement and sheet resistance relation, the laser condition set of 20 ~ 27 % of power, 150 ~ 160 kHz, 20 ~ 50 mm/s of marking speed, and $10\;{\sim}\;50 {\mu}m$ spacing with continuous wave mode of scanner lens showed the correlation between lifetime and sheet resistance as $100\;{\Omega}/sq$ and $11.8\;{\mu}s$ vs. $17\;{\Omega}/sq$ and $8.2\;{\mu}s$. Comparing to the singly deposited p-a-Si:H layer case, the additional ${\mu}c$-Si:H layer for doping resulted in no trade-offs, but showed slight improvement of both lifetime and sheet resistance, however sheet resistance might be confined by the additional intrinsic layer. This might come from the ineffective crystallization of amorphous silicon layer. For the additional layer case, lifetime and sheet resistance were measured as $84.8\;{\Omega}/sq$ and $11.09\;{\mu}s$ vs. $79.8\;{\Omega}/sq$ and $11.93\;{\mu}s$. The co-existence of $n^+$layeronthesamesurfaceandeliminating the laser damage should be taken into account for an IBC solar cell structure. Heavily doped uniform boron layer by fiber laser brings not only basic and essential conditions for the beginning step of IBC solar cell fabrication processes, but also the controllable doping concentration and depth that can be established according to the deposition conditions of layers.

• Transactions on Electrical and Electronic Materials
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• v.13 no.4
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• pp.192-195
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• 2012

We reported diborane ($B_2H_6$) doped wide bandgap hydrogenated amorphous silicon oxide (p-type a-SiOx:H) films prepared by using silane ($SiH_4$) hydrogen ($H_2$) and nitrous oxide ($N_2O$) in a radio frequency (RF) plasma enhanced chemical vapor deposition (PECVD) system. We improved the $E_{opt}$ and conductivity of p-type a-SiOx:H films with various $N_2O$ and $B_2H_6$ ratios and applied those films in regards to the a-Si thin film solar cells. For the single layer p-type a-SiOx:H films, we achieved an optical band gap energy ($E_{opt}$) of 1.91 and 1.99 eV, electrical conductivity of approximately $10^{-7}$ S/cm and activation energy ($E_a$) of 0.57 to 0.52 eV with various $N_2O$ and $B_2H_6$ ratios. We applied those films for the a-Si thin film solar cell and the current-voltage characteristics are as given as: $V_{oc}$ = 853 and 842 mV, $J_{sc}$ = 13.87 and 15.13 $mA/cm^2$. FF = 0.645 and 0.656 and ${\eta}$ = 7.54 and 8.36% with $B_2H_6$ ratios of 0.5 and 1% respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.11
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• pp.841-845
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• 2013

We give a textured front on silicon wafer for high-efficiency solar cells by using micro contact printing method which uses PDMS (polydimethylsiloxane) silicon rubber as a stamp and SAM (self assembled monolayer)s as an ink. A random pyramidal texturing have been widely used for a front-surface texturing in low cost manufacturing line although the cell with random pyramids on front surface shows relatively low efficiency than the cell with inverted pyramids patterned by normal optical lithography. In the past two decades, the micro contact printing has been intensively studied in nano technology field for high resolution patterns on silicon wafer. However, this promising printing technique has surprisingly never applied so far to silicon based solar cell industry despite their simplicity of process and attractive aspects in terms of cost competitiveness. We employ a MHA (16-mercaptohexadecanoic acid) as an ink for Au deposited $SiO_2/Si$ substrate. The $SiO_2$ pattern which is same as the pattern printed by SAM ink on Au surface and later acts as a hard resist for anisotropic silicon etching was made by HF solution, and then inverted pyramidal pattern is formed after anisotropic wet etching. We compare three textured surface with different morphology (random texture, random pyramids and inverted pyramids) and then different geometry of inverted pyramid arrays in terms of reflectivity.