• 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).

• Current Applied Physics
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• v.18 no.12
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• pp.1583-1591
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• 2018

We analysed perovskite $CH_3NH_3PbI_{3-x}Cl_x$ inverted planer structure solar cell with nickel oxide (NiO) and spiroMeOTAD as hole conductors. This structure is free from electron transport layer. The thickness is optimized for NiO and spiro-MeOTAD hole conducting materials and the devices do not exhibit any significant variation for both hole transport materials. The back metal contact work function is varied for NiO hole conductor and observed that Ni and Co metals may be suitable back contacts for efficient carrier dynamics. The solar photovoltaic response showed a linear decrease in efficiency with increasing temperature. The electron affinity and band gap of transparent conducting oxide and NiO layers are varied to understand their impact on conduction and valence band offsets. A range of suitable band gap and electron affinity values are found essential for efficient device performance.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.36.1-36.1
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• 2010

While the substrate-type solar cells with Cu(In,Ga)Se2 absorbers yield conversion efficiencies of up 20%[1], the highest published efficiency of Cu(In,Ga)Se2 superstrate solar cell is only 12.8% [2]. The commerciallized Cu(In,Ga)Se2 solar cells are made in the substrate configuration having the stacking sequence of substrate (soda lime glass)/back contact (molybdenum)/absorber layer (Cu(In,Ga)Se2)/buffer layer (cadmium sulfide)/window layer (transparent conductive oxide)/anti reflection layer (MgF2) /grid contact. Thus, it is not possible to illuminate the substrate-type cell through the glass substrate. Rather, it is necessary to illuminate from the opposite side which requires an elaborate transparent encapsulation. In contrast to that, the configuration of superstrate solar cell allows the illumination through the glass substrate. This saves the expensive transparent encapsulation. Usually, the high quality Cu(In,Ga)Se2 absorber requires a high deposition temperature over 550C. Therefore, the front contact should be thermally stable in the temperature range to realize a successful superstrate-type solar cell. In this study, it was tried to make a decent superstrate-type solar cell with the thermally stable ZnO:Al layer obtained by adjusting its deposition parameters in magnetron sputtering process. The effect of deposition condition of the layer on the cell performance will be discussed together with hall measurement results and current-voltage characteristics of the cells.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.122.2-122.2
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• 2011

결정질 태양전지 제작에서, passavtion은 표면의 반사도를 줄여주는 반사 방지막의 역할과 표면의 dangling bond를 감소시켜, 표면 재결합 속도를 줄이고 minority carrier lifetime을 증가하는 데 큰 영향을 미친다. 그렇기 때문에 저가형 고효율 태양전지 제작에서 우수한 특성을 가지는 passivation막은 매우 중요한 이슈이다. 본 연구에서는 LBC(local back contact) 구조를 가지는 단결정 태양전지 후면에, 기존의 Full Al-BSF의 passivation 막을 SiNx와 ONO passivation 막으로 각각 대체하여, LBC 구조에서 더 적합한 passivation 막을 찾고자 하였다. SiNx와 ONO passivation 막은 단결정 LBC 구조 태양전지 후면에 각각 형성되었고 $800^{\circ}C$, 20 sec 조건으로 소성되었다. 실험결과는 minority carrier lifetime과 surface recombination velocity로 관찰하였다. 그 결과, SiNx passivation 막의 표면 재결합 속도는 29.7cm/s이고, ONO passivation 막의 표면 재결합 속도는 24.5cm/s로, Full Al-BSF 표면 재결합 속도 750cm/s에 비해 더 적합한 passivation 막으로 확인할 수 있었다. 결과적으로 SiNx,ONO passivation 막이 Full Al-BSF보다 전극에 수집되는 캐리어의 양이 많아짐에 따라 효율향상을 가져올 수 있을 것이다.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.603-603
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• 2012

최근에 전면 emitter의 doping profile이 다른 selective emitter solar cell은 실제 제작시단파장 영역에서 많은 gain을 얻을 수 없어 LBC 구조의 태양전지에 관한 연구가 많이 진행되고 있다. 본 연구는 TCAD simulation을 이용하여 후면에 형성되는 locally doped BSF(p++) region의 doping profile의 변화에 따른 태양전지 특성에 관한 연구이다. Al으로 형성되는 local back contact의 doping depth 및 surface concentration에 따른 전기적, 광학적 분석을 통해 주도적인 인자를 분석하고 최적화하였다. 특히 doping depth에 따른 변화보다는 surface concentration의 변화에 따른 특성변화가 주도적으로 나타났다.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.230-230
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• 2007

• Journal of the Speleological Society of Korea
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• no.82
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• pp.5-7
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• 2007

In this paper, p-n junction formation using screen-printed metalization and co-firing is used to fabricate high-efficiency solar cells on single- crystalline silicon substrates. In order to form high-quality contacts, co-firing of a screen-printed Ag grid on the front and Al on the back surface field is implemented. These contacts require low contact resistance, high conductivity, and good adhesion to achieve high efficiency. Before co-firing, a statistically designed experiment is conducted. After the experiment, a neural network (NN) trained by the error back-propagation algorithm is employed to model the crucial relationships between several input factors and solar cell efficiency. The trained NN model is also used to optimize the beltline furnace process through genetic algorithms.

• Journal of the Microelectronics and Packaging Society
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• v.10 no.2
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• pp.33-37
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• 2003

The new textured surface epitaxial base(TSEB) cell as a high efficiency Si solar cell was fabricated and its eletro-optical characteristics were investigated. The fabricated device showed the open circuit voltage of 0.62 V, the short circuit current of 40 mA, the fill factor of 0.7, and the efficiency of 16% under the incident light of AM-1 100 mW/$cm^2$. The TSEB cell proposed in this paper has the structural superiority in the fabrication of high efficiency solar cell due to the carrier drift transport in the optical absorption region and the formation of back surface field by $P^-/P^+$ epitaxial base, and the low emitter series resistance by insertion of $n^+$ buried contact.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.436-437
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• 2008

Flexible CIGS thin film solar cell was fabricated using STS430 plate as a flexible substrate in this work. A diffusion barrier layer of $SiO_2$ thin film was deposited on STS430 substrate by PECVD followed by deposition of double layered Mo back contact. After depositing CIGS absorber layer by co-evaporation, CdS buffer layer by chemical bath deposition, ZnO window layer by RF sputtering and Al electrode by thermal evaporation, the solar cell fabrication processes were completed and its performance was evaluated. Corresponding solar cell showed an conversion efficiency of 8.35 % with $V_{OC}$ of 0.52 V, $J_{SC}$ of 26.06 mA/$cm^2$ and FF of 0.61.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1380-1381
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• 2011

본 논문에서는 SILVACO 사의 ATHENA와 ATLAS를 이용하여 후면 전극 실리콘 태양전지 (back contact silicon solar cell)의 전면 텍스쳐링 (texturing) 깊이 (depth)와 텍스쳐링 간격 (gap)에 따른 태양전지 효율(efficiency)에 미치는 영향을 분석하였다. 제안한 후면 전극 실리콘 태양전지는 (100) silicon wafer(n-type, $6{\times}10^{15}\;cm^{-3}$)을 기반으로 전면부에 텍스쳐링을, 후면부에 BSF(back surface field, $1{\times}10^{20}\;cm^{-3}$)와 에미터(emitter, $8.5{\times}10^{19}\;cm^{-3}$)를 구성하고, 셀간 피치를 1250 ${\mu}m$, BSF와 에미터의 간격을 25 ${\mu}m$으로 한 구조이다. 텍스쳐링 간격이 없이 텍스쳐링 깊이를 0 ${\mu}m$에서 150 ${\mu}m$으로 증가시켜 분석한 결과, 텍스쳐링 깊이가 증가할수록 효율이 23.90%에서 25.79%로 증가하였다. 텍스쳐링 간격을 1 ${\mu}m$에서 100 ${\mu}m$으로 증가시켜 분석한 결과, 텍스쳐링 깊이와 상관없이 텍스쳐링 간격이 증가할수록 후면 전극 실리콘 태양전지의 효율이 감소하였다. 텍스쳐링 유무에 따라 후면 전극 태양전지의 외부양자효율의 차이를 보였고 텍스쳐링이 있을 때 외부양자효율이 보다 높은 값을 얻었다.