• Korean Journal of Materials Research
• /
• v.30 no.10
• /
• pp.509-514
• /
• 2020

The two key variables of an Si solar cell, i.e., emitter (n-type window layer) and base (p-type substrate) doping levels or concentrations, are studied using Medici, a 2-dimensional semiconductor device simulation tool. The substrate is p-type and 150 ㎛ thick, the pn junction is 2 ㎛ from the front surface, and the cell is lit on the front surface. The doping concentration ranges from 1 × 10¹⁰ cm^-3 to 1 × 10²⁰ cm^-3 for both emitter and base, resulting in a matrix of 11 by 11 or a total of 121 data points. With respect to increasing donor concentration (Nd) in the emitter, the open-circuit voltage (Voc) is little affected throughout, and the short-circuit current (Isc) is affected only at a very high levels of Nd, exceeding 1 × 10¹⁹ cm^-3, dropping abruptly by about 12%, i.e., from Isc = 6.05 × 10^-9 A·㎛^-1, at Nd = 1 × 10¹⁹ cm^-3 to Isc = 5.35 × 10^-9 A·㎛^-1 at Nd = 1 × 10²⁰ cm^-3, likely due to minority-carrier, or hole, recombination at the very high doping level. With respect to increasing acceptor concentration (Na) in the base, Isc is little affected throughout, but Voc increases steadily, i.e, from Voc = 0.29 V at Na = 1 × 10¹² cm^-3 to 0.69 V at Na = 1 × 10¹⁸ cm^-3. On average, with an order increase in Na, Voc increases by about 0.07 V, likely due to narrowing of the depletion layer and lowering of the carrier recombination at the pn junction. At the maximum output power (Pmax), a peak value of 3.25 × 10^-2 W·cm^-2 or 32.5 mW·cm^-2 is observed at the doping combination of Nd = 1 × 10¹⁹ cm^-3, a level at which Si is degenerate (being metal-like), and Na = 1 × 10¹⁷ cm^-3, and minimum values of near zero are observed at very low levels of Nd ≤ 1 × 10¹³ cm^-3. This wide variation in Pmax, even within a given kind of solar cell, indicates that selecting an optimal combination of donor and acceptor doping concentrations is likely most important in solar cell engineering.

• Journal of Sensor Science and Technology
• /
• v.5 no.5
• /
• pp.1-10
• /
• 1996

Solar cells made of the edge-defined film-fed growth Si are characterized using current-voltage, surface photovoltage, electron beam induced current, electron microprobe, scanning electron microscopy, and electron backscattering. The weak temperature dependence of the I-V curves in the EFG solar cells is due to a voltage variable shunt resistance giving higher diode ideality factors than the ideal one. The voltage variable shunt resistance is modeled by a modified recombination mechanism which includes carrier tunneling to distributed impurity energy states in the band gap within the space-charge region. The junction integrity and the substrate quality are characterized simultaneously by combining I-V and surface photovoltage (SPV) measurements. The diode ideality factors and the surface photovoltages characterize the junction integrity while the SPV diffusion lengths characterizes the substrate quality. Most of the measured samples show the voltage variable shunt resistance although how serious it is depends on the solar cell efficiency. The voltage variable shunt resistance is understood as one of the most important factors of the degradation of EFG solar cells.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.11 no.7
• /
• pp.2565-2569
• /
• 2010

It was researched the correlation between the Solar cell and the effect of texturing. The samples were textured by using the IPA mixed solution with $HNO_3$, KOH and NaOH. The samples were analyzed by the X-ray Diffraction pattern and Fourier Transform Infrared spectroscopy. The FTIR spectra in the range of 950~1350 $cm^{-1}$ was related to the peak's formation as the bonding structure. The split of peaks means that the inter reaction between the molecular did not activate and then increased the efficiency because of low reflectance as shown the cell treated in NaOH mixed solution.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.12 no.6
• /
• pp.2735-2738
• /
• 2011

To obtain the Si solar cells, the Si-wafers were textured by using the IPA+DI water mixed solution with KOH acids during the various 1~40 minutes at the temperature with $80^{\circ}C$, respectively. The samples were analyzed by the scanning electron microscopy for the surface images and the solar simulation for I-V measurement system. It was researched the correlation between the efficiency of solar cells and the effect of texturing. From the results of the surface images obtained by SEM, the efficiency was increased at the sample textured uniformly, and the efficiency of over etched-samples decreased.

• Korean Journal of Materials Research
• /
• v.28 no.1
• /
• pp.38-42
• /
• 2018

Continuous efforts are being made to improve the efficiency of Si solar cells, which is the prevailing technology at this time. As opposed to the standard front-lit solar cell design, the back-lit design suffers no shading loss because all the metal electrodes are placed on one side close to the pn junction, which is referred to as the front side, and the incoming light enters the denuded back side. In this study, a systematic comparison between the two designs was conducted by means of computer simulation. Medici, a two-dimensional semiconductor device simulation tool, was utilized for this purpose. The $0.6{\mu}m$ wavelength, the peak value for the AM-1.5 illumination, was chosen for the incident photons, and the minority-carrier recombination lifetime (${\tau}$), a key indicator of the Si substrate quality, was the main variable in the simulation on a p-type $150{\mu}m$ thick Si substrate. Qualitatively, minority-carrier recombination affected the short circuit current (Isc) but not the opencircuit voltage (Voc). The latter was most affected by series resistance associated with the electrode locations. Quantitatively, when ${\tau}{\leq}500{\mu}s$, the simulation yielded the solar cell power outputs of $20.7mW{\cdot}cm^{-2}$ and $18.6mW{\cdot}cm^{-2}$, respectively, for the front-lit and back-lit cells, a reasonable 10 % difference. However, when ${\tau}$ < $500{\mu}s$, the difference was 20 % or more, making the back-lit design less than competitive. We concluded that the back-lit design, despite its inherent benefits, is not suitable for a broad range of Si solar cells but may only be applicable in the high-end cells where float-zone (FZ) or magnetic Czochralski (MCZ) Si crystals of the highest quality are used as the substrate.

• 한국신재생에너지학회:학술대회논문집
• /
• 2011.05a
• /
• pp.124.1-124.1
• /
• 2011

결정질 태양전지에서 도핑(Doping)은 반도체(Semiconductor)의 PN 접합(Junction)을 형성하는 중요한 역할을 한다. 도핑은 반도체에 불순물(Dopant)을 주입하는 공정으로 고온에서 진행되며 온도는 중요한 변수(Parameter)로 작용한다. 본 연구에서는 여러 가지 도핑 방법 중 SOD(Spin-On Dopant)를 이용하여 온도에 따른 도핑 결과와 특성을 분석 하였다. P-type 웨이퍼(Wafer)에 SOD를 이용하여 불순물을 증착 후 Hot-plate에서 15분간 Baking 하였다. Baking된 웨이퍼는 노(Furnace)에 넣고 $860^{\circ}C{\sim}880^{\circ}C$까지 $10^{\circ}C$씩 가변하였다. 각각의 조건에 대해 Lifetime과 Sheet Resistance을 측정하였고, 그 결과 $880^{\circ}C$에서의 Lifetime이 $23.58{\mu}s$로 $860^{\circ}C$에 비해 235.8% 증가하여 가장 우수 하였으며, Sheet Resistance 또한 $68{\Omega}$/sq로 $860^{\circ}C$에서 가장 우수하게 측정되었다. SOD의 속도 가변에 따른 특성 변화를 보기 위해 온도는 $880^{\circ}C$에 고정한 후 속도를 3000rpm~4500rpm까지 500rpm간격으로 1시간동안 실험한 결과 rpm 속도에 따른 lifetime 변화는 거의 없었으며, Sheet Resistance는 3000rpm에서 $63{\Omega}$/sq로 가장 우수 하였다. 본 연구를 통해 온도와 Spin rpm에 따른 특성을 확인한 결과 온도가 높을 때 Sheet Resistance가 가장 안정화 되며, lifetime이 더욱 우수한 것을 확인할 수 있었다.

• Journal of the Korean Society of Radiology
• /
• v.3 no.1
• /
• pp.11-15
• /
• 2009

In this study, the basic research verifying possibility of applications as radiology image sensor in Digital Radiography was performed, the radiology image sensor was fabricated using a multi-layer technique to decrease dark current. High efficiency materials in substitution for Amorphous Selenium(a-Se) have been studied as a direct method of imaging detector in Digital Radiography to decrease dark current by using PN junction or Hetero junction already used as solar cell, semiconductor. Particle-In -Binder method is used to fabricate radiology image sensor because it has a lot of advantages such as fabrication convenient, high yield, suitability for large area sensor. But high leakage current is one of main problem in Particle-In -Binder method. To make up for the weak points, multi-layer technique is used, and it is considered that high efficient digital radiation sensor can be fabricated with easy and convenient process. In this study, electrical properties such as leakage current, sensitivity, signal linearity is measured to evaluate multi-layer radiation sensor material.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.08a
• /
• pp.406-406
• /
• 2011

결정질 태양전지에서 도핑(Doping)은 반도체(Semiconductor)의 PN 접합(Junction)을 형성하는 중요한 역할을 한다. 도핑은 반도체에 불순물(Dopant)을 주입하는 공정으로 고온에서 진행되며 온도는 중요한 변수(Parameter)로 작용한다. 본 연구에서는 여러 가지 에미터(emitter)층 형성방법 중에 가장 저가이면서 공정과정이 간단하며 대면적 도핑이 용의한 Spray 방법을 통해 효과적인 에미터 층 형성의 최적화를 위해 DI water에 각각 1%, 3%, 5% 7%로 희석된 H3PO4용액 으로 850$^{\circ}C$에서 열처리 시간을 가변해 가며 최적화된 면저항과 표면농도 특성을 분석하였다. 도핑소스가 웨이퍼(wafer) 각각의 표면에 흡착시킨 후 오븐에 넣어 150$^{\circ}C$에서 5분간 건조시킨 후 퍼니스(furance)에 넣어 시간을 가변해 가며 도핑시켰다. Spray 방식은 기존의 방식보다 저렴하고 In-line 공정에 적합하며 대용량으로 전환이 쉽다는 많은 장점을 가지고 있다. 도핑시 먼저 spray를 이용하여 웨이퍼 표면에 균일하게 용액을 흡착시킨 후 오븐에서 150$^{\circ}C$에서 5분간 건조 후 furnace에 넣어 850$^{\circ}C$에서 시간을 가변 해가며 실험하였다. H3PO4용액의 비율이 1%일 때는 2분 이상 열처리를 하였을 때 60${\Omega}/{\Box}$ 이하로 내려가지 않았다. 이는 최초 표면농도가 낮아 더 이상 확산되지 않음을 의미한다. 또한 H3PO4의 비율이 3% 이상일 때는 열처리 시간이 1분 이하일 때 면저항의 변화가 거의 없었으나 2분 이상일 때는 시간에 따라서 점차 낮아졌으며 균일도 역시 좋아졌다. 이는 H3PO4의 비율이 3% 이상일 때는 표면농도가 높아서 1분 이하의 열처리 시간에서는 확산해 들어가는 양이 거의 같음을 알 수 있었다.