• Current Photovoltaic Research
• /
• v.9 no.3
• /
• pp.75-83
• /
• 2021

The tunnel oxide passivated contact (TOPCon) structure got more consideration for development of high performance solar cells by the introduction of a tunnel oxide layer between the substrate and poly-Si is best for attaining interface passivation. The quality of passivation of the tunnel oxide layer clearly depends on the bond of SiO in the tunnel oxide layer, which is affected by the subsequent annealing and the tunnel oxide layer was formed in the suboxide region (SiO, Si₂O, Si₂O₃) at the interface with the substrate. In the suboxide region, an oxygen-rich bond is formed as a result of subsequent annealing that also improves the quality of passivation. To control the surface morphology, annealing profile, and acceleration rate, an oxide tunnel junction structure with a passivation characteristic of 700 mV or more (V_oc) on a p-type wafer could achieved. The quality of passivation of samples subjected to RTP annealing at temperatures above 900℃ declined rapidly. To improve the quality of passivation of the tunnel oxide layer, the physical properties and thermal stability of the thin layer must be considered. TOPCon silicon solar cell has a boron diffused front emitter, a tunnel-SiO_x/n⁺-poly-Si/SiN_x:H structure at the rear side, and screen-printed electrodes on both sides. The saturation currents J_o of this structure on polished surface is 1.3 fA/cm² and for textured silicon surfaces is 3.7 fA/cm² before printing the silver contacts. After printing the Ag contacts, the J_o of this structure increases to 50.7 fA/cm² on textured silicon surfaces, which is still manageably less for metal contacts. This structure was applied to TOPCon solar cells, resulting in a median efficiency of 23.91%, and a highest efficiency of 24.58%, independently. The conversion efficiency of interdigitated back-contact solar cells has reached up to 26% by enhancing the optoelectrical properties for both-sides-contacted of the cells.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2007.11a
• /
• pp.321-322
• /
• 2007

In order to increase the cost effectiveness of solar cells, module production should be treated more comprehensively. Back contact cells offer distinct advantage in the interconnection of cells to modules. Thereby Mo thin film were prepared in order to clarify optimum conditions for growth of the thin film depending upon process, and then by changing a number of deposition conditions and substrate temperature conditions variously, structural and electrical characteristics were measured. For the manufacture of the Mo were vapor-deposited in the named order. Among them, Mo were vapor-deposited by using the sputtering method in consideration of their adhesive force to the substrate, and the DC power was controlled so that the composition of Mo, while the surface temperature having an effect on the quality of the thin film was changed from R.T$[^{\circ}C]$ to $200[^{\circ}C]$ at intervals of $50[^{\circ}C]$. Micro-structural studies were carried out by XRD (D/MAX-1200, Rigaku Co.) and SEM (JSM-5400, Jeol Co.). Electrical properties were measured by CMT-SR3000 Measurement System.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.02a
• /
• pp.420-420
• /
• 2011

결정질 태양전지에서 고효율 달성을 위한 LBC(Local Back Contact) 구조의 중요성이 강조되고 있다. LBC 구조에서 후면 passivation 형성을 위한 SiNX layer를 PECVD로 형성 시, 실리콘 bulk 내로 H+ 원자가 침투하여 Boron과 결합하게 되면 Boron이 bulk 내에서 dopant로 작용을 하지 못하게 되어, 후면에서 p-층을 형성하고, 이는 VOC의 저하를 야기 시킨다. 본 연구에서는 LBC 구조에서 후면 passivation 시 bluk 내 B-H결합으로 인한 태양전지 특성 저하 문제를 해결하기 위해, SiNX를 증착하기 전에 얇은 산화막 barrier를 성장시켜 Bulk 내에 H+ 침투를 최소화 하였다. PECVD를 이용한 N2O 플라즈마 처리, HNO3 Wet Chemical Oxidation의 방법을 통해 substrate와 SiNX 사이에 얇은 oxide 층을 형성하였으며, 각각의 조건에 대해 lifetime 측정을 실시하였다. 그 결과 SiON/SiNx를 이용한 막의 lifetime이 $94.5{\mu}s$로 가장 우수하였고, Reference에 비해 25.4% 증가함을 확인할 수 있었다. 그러나 HNO3/SiNx에서는 30.6%, SiON에서는 84.3% 감소함을 확인하였다. Voc 측정 결과 또한 SiON/SiNx를 이용한 막이 670mV로 가장 우수함을 확인할 수 있었다. 본 연구를 통해 LBC구조에서 후면에 얇게 SiON/SiNx막을 형성함으로서 H+이온의 침투를 저지하여 후면 B-H결합을 막아 태양전지 특성 저하를 감소시키는 것을 확인할 수 있었다.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.08a
• /
• pp.325-325
• /
• 2010

최근 결정질 실리콘 태양전지 분야에서는 태양전지의 Voc와 Isc의 증가를 통한 효율 향상을 목적으로 후면 passivation에 대한 연구가 활발하게 진행되고 있다. Local-Back Contact은 최적화된 후면 passivation 박막을 이용한 태양전지 제조방법이다. 고효율 태양전지 개발을 위해 최적의 laser 가공 조건이 확립되어야 한다. 본 연구에서는 고효율의 LBC 태양전지 개발을 위해 ONO 구조의 후면 passivation 박막에 laser ablation 조건을 가변하여 LBC 태양전지를 제작하고 그 특성을 분석하였다. 본 연구에 사용된 laser는 355nm 파장을 갖는 UV laser를 사용하였다. laser 파워는 5W, 주파수는 30kHz로 하였을 때 폭 20um, 깊이 5um의 홀을 형성시킬 수 있었다. 후면 접촉 면적의 영향을 확인하기 위하여 laser ablation 간격을 300um, 500um, 700um으로 가변하여 공정을 진행하였다. 태양전지 제조 결과 spacing 300um일 경우 효율이 높게 측정되었으며, laser ablation의 데미지를 줄이기 위한 FGA 처리시 웨이퍼 표면의 데미지를 줄여 carrier lifetime 향상에 기여하는 것을 확인할 수 있었다. 본 연구의 결과를 이용하여 향후 후면 passivation 극대화 및 접촉면적 가변을 통한 고효율 LBC 태양전지 개발이 가능할 것으로 판단된다.

• 한국태양에너지학회:학술대회논문집
• /
• 2011.11a
• /
• pp.51-55
• /
• 2011

In this paper, the optimized doping condition of crystalline silicon solar cells with 156 ${\times}$ 156 mm2 area was studied. To optimize the drive-in condition in the doping process, the other conditions except drive-in temperature and time were fixed. After etching 7 ${\mu}m$ of the surface to form the pyramidal structure, the silicon nitride deposited by the PECVD had 75~80 nm thickness and 2 to 2.1 for a refractive index. The silver and aluminium electrodes for front and back sheet, respectively, were formed by screen-printing method, followed by firing in $400-425-450-550-850^{\circ}C$ five-zone temperature conditions to make the ohmic contact. Drive-in temperature was changed in range of $828^{\circ}C$ to $860^{\circ}C$ and time was from 3 min to 40 min. The sheet resistance of wafer was fixed to avoid its effect on solar cell. The solar cell fabricated with various conditions showed the similar conversion efficiency of 17.4%. This experimental result showed the drive-in temperatures and times little influence on solar cell characteristics.

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

• Journal of the Korean institute of surface engineering
• /
• v.44 no.6
• /
• pp.264-268
• /
• 2011

The Molybedenium thin film is generally used on back contact material of CIGS solar cell due to low electrical resistivity and stable thermal expansion coefficient. The Mo thin films deposited on si wafer by the magnetron sputtering method. The research focused on the variation of electrical resistivity of films which deposited with various working pressure at the target power of 2.0 kW(8.4 W/). The lowest resistivity of Mo thin film showed $9.0{\mu}O$-cm at pressure of 1.5 mTorr. However, working pressure increasing up to 50 mTorr, resistivities were highly increased. The results showed that the conductivity of Mo films depended on growing structures and defects in deposition process. Surface morphology, porosity, grain size, oxidation, and bonding structures were analysed by SEM, AFM, spectroscopic ellipsometry (SE), XRD, and XPS.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.58 no.11
• /
• pp.2214-2218
• /
• 2009

Dye-sensitized solar cell (DSC) has been considered as a possible alternative to current silicon based p-n junction photovoltaic devices due to its advantages of high efficiency, simple fabrication process and low production cost. Numerous researches for high efficient DSC in the various fields are under way even now. Among them, the compact layer, which prevents the back electron transfer between transparent conductive oxides and the redox electrolyte, is fabricated by various methods such as a ZnO dip-coating, $TiCl_4$ dip-coating, and Ti sputtering. In this study, we tried to fabricate the $TiO_2$ compact layer by the spin-coating method using aqueous $TiCl_4$ solution. The effect of the spin-coating method was checked as compared with conventional dip-coating method. As a result, DSC with a spin-coated compact layer had 33.4% and 6% better efficiency than standard DSC and DSC with a dip-coated compact layer.

• 한국신재생에너지학회:학술대회논문집
• /
• 2008.05a
• /
• pp.402-405
• /
• 2008

SunPower's corporate mission is to reduce the installed cost of solar electricity 50% by 2012. As part of that mission, the company is continually exploring novel technologies that might enable progress towards the goal. This paper describes SunPower's efforts to decrease the levelized cost of electricity for solar power plants through the use of bifacial cell and system technology. The results of the first production run of SunPower bifacial cells and modules are presented. Future bifacial system development plans are reviewed.

• Korean Journal of Materials Research
• /
• v.26 no.8
• /
• pp.422-426
• /
• 2016

With the increase in installed solar energy capacity, comparison and analysis of the physical property values of solar cells are becoming increasingly important for production. Therefore, research on determining the physical characteristic values of solar cells is being actively pursued. In this study, a diode equation, which is commonly used to describe the I-V behavior and determine the electrical characteristic values of solar cells, was applied. Using this method, it is possible to determine the diode ideality factor (n) and series resistance ($R_s$) based on light I-V measurements. Thus, using a commercial screen-printed solar cell and an interdigitated back-contact solar cell, we determined the ideality factor (n) and series resistance ($R_s$) with a modified diode equation method for the light I-V curves. We also used the sun-shade method to determine the ideality factor (n) and series resistance ($R_s$) of the samples. The values determined using the two methods were similar. However, given the error in the sun-shade method, the diode equation is considered more useful than the sun-shade method for analyzing the electrical characteristics because it determines the ideality factor (n) and series resistance ($R_s$) based on the light I-V curves.