• 한국재료학회지
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• 제20권4호
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• pp.210-216
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• 2010

This paper investigates the dependence of a-Si:H/c-Si passivation and heterojunction solar cell performances on various cleaning processes of silicon wafers. It is observed that the passivation quality of a-Si:H thin-films on c-Si wafers depends highly on the initial H-termination properties of the wafer surface. The effective minority carrier lifetime (MCLT) of highly H-terminated wafer is beneficial for obtaining high quality passivation of a-Si:H/c-Si. The wafers passivated by p(n)-doped a-Si:H layers have low MCLT regardless of the initial H-termination quality. On the other hand, the MCLT of wafers incorporating intrinsic (i) a-Si:H as a passivation layer shows sensitive variation with initial cleaning and H-termination schemes. By applying the improved cleaning processes, we can obtain an MCLT of $100{\mu}sec$ after H-termination and above $600{\mu}sec$ after i a-Si:H thin film deposition. By adapting improved cleaning processes and by improving passivation and doped layers, we can fabricate a-Si:H/c-Si heterojunction solar cells with an active area conversion efficiency of 18.42%, which cells have an open circuit voltage of 0.670V, short circuit current of $37.31\;mA/cm^2$ and fill factor of 0.7374. These cells show more than 20% pseudo efficiency measured by Suns-$V_{oc}$ with an elimination of series resistance.

• 한국재료학회지
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• 제21권6호
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• pp.341-346
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• 2011

In this study, we inserted a Zn buffer layer into a AZO/p-type a-si:H layer interface in order to lower the contact resistance of the interface. For the Zn layer, the deposition was conducted at 5 nm, 7 nm and 10 nm using the rf-magnetron sputtering method. The results were compared to that of the AZO film to discuss the possibility of the Zn layer being used as a transparent conductive oxide thin film for application in the silicon heterojunction solar cell. We used the rf-magnetron sputtering method to fabricate Al 2 wt.% of Al-doped ZnO (AZO) film as a transparent conductive oxide (TCO). We analyzed the electro-optical properties of the ZnO as well as the interface properties of the AZO/p-type a-Si:H layer. After inserting a buffer layer into the AZO/p-type a-Si:H layers to enhance the interface properties, we measured the contact resistance of the layers using a CTLM (circular transmission line model) pattern, the depth profile of the layers using AES (auger electron spectroscopy), and the changes in the properties of the AZO thin film through heat treatment. We investigated the effects of the interface properties of the AZO/p-type a-Si:H layer on the characteristics of silicon heterojunction solar cells and the way to improve the interface properties. When depositing AZO thin film on a-Si layer, oxygen atoms are diffused from the AZO thin film towards the a-Si layer. Thus, the characteristics of the solar cells deteriorate due to the created oxide film. While a diffusion of Zn occurs toward the a-Si in the case of AZO used as TCO, the diffusion of In occurs toward a-Si in the case of ITO used as TCO.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.28-30
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• 2009

이종접합태양전지에서 p a-Si:H/c-Si의 p a-Si:H의 증착 조건인 $H_2/SiH_4$ 비율, $B_2H_6$의 농도를 변화 시키며 실험하여 이 따라 계면 특성 변화를 연구하였다. pa-Si:H의 $H_2/SiH_4$ 비율이 상승할수록 carrier lifetime이 증가하다 다시 감소하는 경향을 나타내었다. 이는 $H_2/SiH_4$의 비율 중 효과적으로 웨이퍼표면을 효과적으로 passivation하는 지점이 있는 것으로 보인다. $B_2H_6$의 농도는 상승할수록 carrier lifetime이 줄어드는 경향을 보였다. $B_2H_6$에서 농도가 올라감에 웨이퍼 표면의 defect로 작용했을 것으로 생각된다. 이에서 몇몇의 조건으로 태양전지를 제작한 결과 $H_2/SiH_4$ 비율에 따라서는 carrier lifetime은 효율에 그 영향이 미미한 것으로 조사되었고, $B_2H_6$의 농도가 낮을수록 개방전압은 상승하는 결과를 얻어 도핑 농도가 효율에 직접적인 형향을 주는 것으로 나타났다.

• 한국진공학회지
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• 제21권1호
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• pp.62-68
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• 2012

건재 일체형 태양광발전(BIPV) 응용을 위해 광 입사각에 따른 태양전지의 변환 효율은 중요하다. 양자효율은 태양전지의 파장별 전자 수집효율을 말하며, 입사각별 양자효율 측정으로 입사각에 따른 태양전지 출력 변화 요인을 분석할 수 있다. 이러한 입사각별 양자효율은 태양전지 종류에 따라 차이를 보인다. 본 연구에서는 가장 많이 쓰이는 벌크형 단결정 실리콘 태양전지와 박막형 비정질 실리콘 태양전지의 입사각별 양자효율을 비교하였다. 그 결과, 단결정 실리콘 태양전지에서는 광 입사각이 증가함에 따라 전 파장영역에서 양자효율이 감소했다. 반면, 비정질 박막 실리콘 태양전지에서는 단파장 영역에서는 결정질 실리콘과 동일하게 감소하였으나, 그 이후의 흡수 영역에서 약 $40^{\circ}$의 입사각까지 증가 또는 일정한 양자효율을 보이다가 이후에 급격히 감소하는 결과를 얻었다. 이는 비정질 박막 실리콘 태양전지에서 입사각이 증가함에 따라 특정 파장 영역에서 산란과 박막 구조의 영향으로 예상된다. 따라서, 태양전지의 구조 및 광학 구조 최적화 등으로 BIPV 적용에 유리한 구조 태양전지 제작이 가능할 것으로 보인다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 D
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• pp.1361-1363
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• 1998

Poly-Si grain boundaries act as potential barriers as well as recombination centers for the photo-generated carriers in solar cells. Thereby, grain boundaries of poly-Si are considered as a major source of the poly-Si cell efficiency was reduced This paper investigated grain boundary effect of poly-Si wafer prior to the solar cell fabrication. By comparing I-V characteristics inner grain, on and across the grain boundary, we were able to detect grain potentials. To reduce grain boundary effect we carried out pretreatment, $POCl_3$ gettering, and examined carrier lifetime. This paper focuses on resistivity variation effect due to grain boundary of poly-Si. The resistivity of the inner grain was $2.2{\Omega}-cm$, on the grain boundary$2.3{\Omega}-cm$, across the grain boundary $2.6{\Omega}-cm$. A measured resistivity varied depending on how many grains were included inside the four point probes. The resistivity increased as the number of grain boundaries increased. Our result can contribute to achieve high conversion efficiency of poly-Si solar cell by overcoming the grain boundary influence.

• Current Photovoltaic Research
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• 제9권3호
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• pp.75-83
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• 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.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.492-492
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• 2014

On account of the good conductivity and optical properties, TCO is generally used in silicon heterojunction solar cell since the emitter material, hydrogenated amorphous silicon (a-Si:H), of the solar cell has low conductivity compare to the emitter of crystalline silicon solar cell. However, the work function mismatch between TCO layer and emitter leads to band-offset and interfere the injection of photo-generated carriers. In this study, work function engineering of TCO by oxygen reactive sputtering method was carried out to identify the trend of band-offset change. The open circuit voltage and short circuit current are noticeably changed by work function that effected from variation of oxygen ratio.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2005년도 춘계학술대회
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• pp.113-116
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• 2005

In this paper, silicon thin-film solar cells(Si- TFSC) and a-Si/c-Si heterojunction solar cells(HJ-cell) are investigated. The Si-TFSC was prepared on glass substrate by depositing $1-3{\mu}m$ thin-film silicons by glow discharge method. The $a-Si:H/{\mu}c-Si:H$ tandem solar cells on textured ZnO:A1 TCO (transparent conducting oxide) showed improved Jsc in top and bottom cells than that on $SnO_2:F$ TCO. This enhancement of jsc resulted from improved light trapping effect by front textured ZnO:A1. The a-Si/c-Si HJ-cells with simple structure without high efficiency features are suffering from low Voc and Jsc. The improvement of front nip and back interface properties by adopting high quality silicon-films at low temperature should be done both for increasing device performances and production cost.

• 한국전기전자재료학회논문지
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• 제25권12호
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• pp.1009-1014
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• 2012

Hydrogenated amorphous silicon (${\alpha}$-Si:H) layers deposited by plasma enhanced chemical vapor deposition (PECVD) are investigated for use in silicon hetero-junction solar cells employing n-type crystalline silicon (c-Si) substrates. The optical and structural properties of silicon hetero-junction devices have been characterized using spectroscopy ellipsometry and high resolution cross-sectional transmission electron micrograph (HRTEM). In addition, the effective carrier lifetime is measured by the quasi-steady-state photocoductance (QSSPC) method. We have studied on the correlation between the order of ${\alpha}$-Si:H and the passivation quality at the interface of ${\alpha}$-Si:H/c-Si. Base on the result, we have fabricated a silicon hetero-junction solar cell incorporating the ${\alpha}$-Si:H passivation layer with on open circuit voltage ($V_{oc}$) of 637 mV.

• 한국전기전자재료학회논문지
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• 제24권9호
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• pp.766-772
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• 2011

Amorphous Si (a-Si) thin films of $p^+/p^-/n^+$ were deposited on $Si_3N_4$/glass substrate by using a plasma enhanced chemical vapor deposition (PECVD) method. These films were annealed at various temperatures and for various times by using a rapid thermal process (RTP) equipment. This step was added before the main thermal treatment to make the nuclei in the a-Si thin film for reducing the process time of the crystallization. The main heat treatment for the crystallization was performed at the same condition of $600^{\circ}C$/18 h in conventional furnace. The open-circuit voltages ($V_{oc}$) were remained about 450 mV up to the nucleation condition of 16min in the nucleation RTP temperature of $680^{\circ}C$. It meat that the process time for the crystallization step could be reduced by adding the nucleation step without decreasing the electrical property of the thin film Si for the solar cell application.