• 한국재료학회지
• /
• 제25권4호
• /
• pp.196-201
• /
• 2015

This paper presents the impact of partial shading on $CuIn_xGa_{(1-x)}Se_2(CIGS)$ photovoltaic(PV) modules with bypass diodes. When the CIGS PV modules were partially shaded, the modules were under conditions of partial reverse bias. We investigated the characterization of the bypass diode and solar cell properties of the CIGS PV modules when these was partially shaded, comparing the results with those for a crystalline silicon module. In crystalline silicon modules, the bypass diode was operated at a partial shade modules of 1.67 % shading. This protected the crystalline silicon module from hot spot damage. In CIGS thin film modules, on the other hand, the bypass diode was not operated before 20 % shading. This caused damage because of hotspots, which occurred as wormlike defects in the CIGS thin film module. Moreover, the bypass diode adapted to the CIGS thin film module was operated fully at 60% shading, while the CIGS thin film module was not operated under these conditions. It is known that the bypass diode adapted to the CIGS thin film module operated more slowly than that of the crystalline silicon module; this bypass diode also failed to protect the module from damage. This was because of the reverse saturation current of the CIGS thin film, $1.99{\times}10^{-5}A/cm^2$, which was higher than that of crystalline silicon, $8.11{\times}10^{-7}A/cm^2$.

• 한국재료학회지
• /
• 제20권11호
• /
• pp.617-622
• /
• 2010

We have studied methods to save Si source during the fabrication process of crystalline Si solar cells. One way is to use a thin silicon wafer substrate. As the thickness of the wafers is reduced, mechanical fractures of the substrate increase with the mechanical handling of the thin wafers. It is expected that the mechanical fractures lead to a dropping of yield in the solar cell process. In this study, the mechanical properties of 220-micrometer-solar grade Cz p-type monocrystalline Si wafers were investigated by varying saw-damage etching conditions in order to improve the flexural strength of ultra-thin monocrystalline Si solar cells. Potassium hydroxide (KOH) solution and tetramethyl ammonium hydroxide (TMAH) solution were used as etching solutions. Etching processes were operated with a varying of the ratio of KOH and TMAH solutions in different temperature conditions. After saw-damage etching, wafers were cleaned with a modified RCA cleaning method for ten minutes. Each sample was divided into 42 pieces using an automatic dicing saw machine. The surface morphologies were investigated by scanning electron microscopy and 3D optical microscopy. The thickness distribution was measured by micrometer. The strength distribution was measured with a 4-point-bending tester. As a result, TMAH solution at $90^{\circ}C$ showed the best performance for flexural strength.

• 한국재료학회지
• /
• 제23권1호
• /
• pp.35-40
• /
• 2013

In this study, the influence on the surface passivation properties of crystalline silicon according to silicon wafer thickness, and the correlation with a-Si:H/c-Si heterojunction solar cell performances were investigated. The wafers passivated by p(n)-doped a-Si:H layers show poor passivation properties because of the doping elements, such as boron(B) and phosphorous(P), which result in a low minority carrier lifetime (MCLT). A decrease in open circuit voltage ($V_{oc}$) was observed when the wafer thickness was thinned from $170{\mu}m$ to $50{\mu}m$. On the other hand, wafers incorporating intrinsic (i) a-Si:H as a passivation layer showed high quality passivation of a-Si:H/c-Si. The implied $V_{oc}$ of the ITO/p a-Si:H/i a-Si:H/n c-Si wafer/i a-Si:H/n a-Si:H/ITO stacked layers was 0.715 V for $50{\mu}m$ c-Si substrate, and 0.704 V for $170{\mu}m$ c-Si. The $V_{oc}$ in the heterojunction solar cells increased with decreases in the substrate thickness. The high quality passivation property on the c-Si led to an increasing of $V_{oc}$ in the thinner wafer. Short circuit current decreased as the substrate became thinner because of the low optical absorption for long wavelength light. In this paper, we show that high quality passivation of c-Si plays a role in heterojunction solar cells and is important in the development of thinner wafer technology.

• JSTS:Journal of Semiconductor Technology and Science
• /
• 제13권6호
• /
• pp.581-588
• /
• 2013

This paper presents a study of the process temperature dependence of $Al_2O_3$ film grown by thermal atomic layer deposition (ALD) as a passivation layer in the crystalline Si (c-Si) solar cells. The deposition rate of $Al_2O_3$ film maintained almost the same until $250^{\circ}C$, but decreased from $300^{\circ}C$. $Al_2O_3$ film deposited at $250^{\circ}C$ was found to have the highest negative fixed oxide charge density ($Q_f$) due to its O-rich condition and low hydroxyl group (-OH) density. After post-metallization annealing (PMA), $Al_2O_3$ film deposited at $250^{\circ}C$ had the lowest slow and fast interface trap density. Actually, $Al_2O_3$ film deposited at $250^{\circ}C$ showed the best passivation effects, that is, the highest excess carrier lifetime (${\tau}_{PCD}$) and lowest surface recombination velocity ($S_{eff}$) than other conditions. Therefore, $Al_2O_3$ film deposited at $250^{\circ}C$ exhibited excellent chemical and field-effect passivation properties for p-type c-Si solar cells.

• Transactions on Electrical and Electronic Materials
• /
• 제1권4호
• /
• pp.11-15
• /
• 2000

This paper presents a process optimization of antireflection (AR) coating on crystalline Si solar cells. Theoretical and experimental investigations were performed on a double-layer AR(DLAR) coating of MgFe$_2$/GeO$_2$. We investigated GeO$_2$ films as an AR layer because they have a proper refractive index of 2.46 and demonstrate the same lattice constant as Si substrate. RF sputter grown GeO$_2$ film showed deposition temperature strong dependence. The GeO$_2$ at 400$\^{C}$ exhibited a strong (111) preferred orientation and the lowest surface roughness of 6.87 $\AA$. Refractive index of MgFe$_2$film was measured as 1.386 for the most of growth temperature. An optimized DLAR coating showed a reflectance as low as 2.04% in the wavelengths ranged from 0.4 ㎛ to 1.1 ㎛. Solar cells with a structure of MgFe$_2$/GeO$_2$/Ag/N$\^$+//p-type Si/P$\^$+//Al were investigated with the without DLAR coatings. We achieved the efficiency of solar cells greater than 15% with 3.12% improvement with DLAR coatings. Further details about MgFe$_2$,GeO$_2$ films, and cell fabrication parameters are presented in this paper.

• 한국재료학회지
• /
• 제21권5호
• /
• pp.243-249
• /
• 2011

To reduce manufacturing costs of crystalline silicon solar cells, silicon wafers have become thinner. In relation to this, the properties of the aluminium-back surface field (Al-BSF) are considered an important factor in solar cell performance. Generally, screen-printing and a rapid thermal process (RTP) are utilized together to form the Al-BSF. This study evaluates Al-BSF formation on a (111) textured back surface compared with a (100) flat back surface with variation of ramp up rates from 18 to $89^{\circ}C$/s for the RTP annealing conditions. To make different back surface morphologies, one side texturing using a silicon nitride film and double side texturing were carried out. After aluminium screen-printing, Al-BSF formed according to the RTP annealing conditions. A metal etching process in hydrochloric acid solution was carried out to assess the quality of Al-BSF. Saturation currents were calculated by using quasi-steady-state photoconductance. The surface morphologies observed by scanning electron microscopy and a non-contacting optical profiler. Also, sheet resistances and bulk carrier concentration were measured by a 4-point probe and hall measurement system. From the results, a faster ramp up during Al-BSF formation yielded better quality than a slower ramp up process due to temperature uniformity of silicon and the aluminium surface. Also, in the Al-BSF formation process, the (111) textured back surface is significantly affected by the ramp up rates compared with the (100) flat back surface.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
• /
• pp.430-430
• /
• 2008

Using multi plasma enhanced chemical vapor deposition system (Multi-PECVD), p-a-Si:H deposition layer as a $p^+$ region which was annealed by laser (Q-switched fiber laser, $\lambda$ = 1064 nm) on an n-type single crystalline Si (100) plane circle wafer was prepared as new doping method for single crystalline interdigitated back contact (IBC) solar cells. As lots of earlier studies implemented, most cases dealt with the excimer (excited dimer) laserannealing or crystallization of boron with the ultraviolet wavelength range and $10^{-9}$ sec pulse duration. In this study, the Q-switched fiber laser which has higher power, longer wavelength of infrared range ($\lambda$ = 1064 nm) and longer pulse duration of $10^{-8}$ sec than excimer laser was introduced for uniformly deposited p-a-Si:H layer to be annealed and to make sheet resistance expectable as an important process for IBC solar cell $p^+$ layer on a polished n-type Si circle wafer. A $525{\mu}m$ thick n-type Si semiconductor circle wafer of (100) plane which was dipped in a buffered hydrofluoric acid solution for 30 seconds was mounted on the Multi-PECVD system for p-a-Si:H deposition layer with the ratio of $SiH_4:H_2:B_2H_6$ = 30:120:30, at $200^{\circ}C$, 50 W power, 0.2 Torr pressure for 20 minutes. 15 mm $\times$ 15 mm size laser cut samples were annealed by fiber laser with different sets of power levels and frequencies. By comparing the results of lifetime measurement and sheet resistance relation, the laser condition set of 50 mm/s of mark speed, 160 kHz of period, 21 % of power level with continuous wave mode of scanner lens showed the features of small difference of lifetime and lowering sheet resistance than before the fiber laser treatment with not much surface damages. Diode level device was made to confirm these experimental results by measuring C-V, I-V characteristics. Uniform and expectable boron doped layer can play an important role to predict the efficiency during the fabricating process of IBC solar cells.

• 한국결정성장학회지
• /
• 제21권6호
• /
• pp.225-229
• /
• 2011

현재 결정질 태양전지에서 웨이퍼 가공은 대부분 슬러리 분사 방식의 다중 와이어를 이용한 방법이 사용되고 있다. 이와 같은 슬러리 분사 방식의 웨이퍼 가공은 가공속도가 낮아 생산성이 떨어지는 단점이 있을 뿐만 아니라 금속 재질의 와이어와 실리콘 블록의 직접적인 마찰에 의하여 웨이퍼 표면의 금속 불순물에 의한 오염이 발생되는 단점이 있다. 뿐만 아니라 와이어와 실리콘 블록간의 직접적인 마찰로 인하여 와이어가 빨리 마모되며, 이로 인하여 일회성의 와이어를 사용하게 되면서 제조원가는 상승하게 된다. 반면에 다이아몬드 입자가 코팅된 와이어를 이용하여 실리콘 웨이퍼를 가공하게 되면, 가공속도가 기존 슬러리 분사방식보다 빠르며, 공정진행에 따른 와이어의 마모율이 적어 와이어의 재사용에 의한 제조원가 절감이 가능하다. 따라서 이와 같은 다이아몬드 입자가 코팅된 와이어를 이용하여 가공하는 기술은 슬러리 분사방식에 비하여 더 효율적이라 할 수 있다. 본 연구에서는 슬러리 분사방식으로 가공된 웨이퍼와 다이아몬드 코팅된 와이어로 가공된 웨이퍼의 표면특성에 대하여 분석하고 셀 공정에 영향을 미치는 것에 대하여 설명하고자 한다. 또한, 다이아몬드 와이어로 가공된 웨이퍼를 활용하기 위한 셀 공정의 개선방향에 대하여 제안하고자 한다.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2009년도 추계학술대회 논문집
• /
• pp.256-256
• /
• 2009

This paper presents a proper condition to achieve above 17 % conversion efficiency using PC1D simulator. Crystalline silicon wafer with thickness of $240{\mu}m$ was used as a starting material. Various efficiency influencing parameters such as rear surface recombination velocity and minority carrier diffusion length in the base region, front surface recombination velocity, junction depth and doping concentration in the Emitter layer. Among the investigated variables, we learn that 2nd doping concentration as a key factor to achieve conversion efficiency higher than 17 %.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
• /
• pp.283.1-283.1
• /
• 2016

Tin Oxide(SnO2) has been widely investigated as a transparent conducting oxide (TCO) and can be used in optoelectronic devices such as solar cell and flat-panel displays. It would be applicable to fabricating the wide bandgap semiconductor because of its bandgap of 3.6 eV. In addition, SnO2 is commonly used as gas sensors. To fabricate high quality epitaxial SnO2 thin films, a powder sputtering method was used, in contrast to typical sputtering technique with sintered target. Single crystalline sapphire(0001) substrates were used. The samples were prepared with varying the growth parameters such as gas environment and film thickness. Then, the samples were characterized by using X-ray diffraction, scanning electron microscopy, and atomic force microscopy measurements. We found that the strain evolution of the samples was highly affected by gas environment and growth rate, resulted in the delamination under O2 environment.