• ETRI Journal
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• v.38 no.2
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• pp.265-271
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• 2016

We analyzed the interface characteristics of Zn-based thin-film buffer layers formed by a sulfur thermal cracker on a $Cu(In,Ga)Se_2$ (CIGS) light-absorber layer. The analyzed Zn-based thin-film buffer layers are processed by a proposed method comprising two processes - Zn-sputtering and cracker-sulfurization. The processed buffer layers are then suitable to be used in the fabrication of highly efficient CIGS solar cells. Among the various Zn-based film thicknesses, an 8 nm-thick Zn-based film shows the highest power conversion efficiency for a solar cell. The band alignment of the buffer/CIGS was investigated by measuring the band-gap energies and valence band levels across the depth direction. The conduction band difference between the near surface and interface in the buffer layer enables an efficient electron transport across the junction. We found the origin of the energy band structure by observing the chemical states. The fabricated buffer/CIGS layers have a structurally and chemically distinct interface with little elemental inter-diffusion.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.301-301
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• 2010

In order to enhance the efficiency of the organic solar cells, the effects of plasma surface treatment with using $CF_4$ and $O_2$ gas on the anode ITO were studied. The polymer solar cell devices were fabricated on ITO glasses an active layer of P3HT (poly-3-hexylthiophene) and PCBM ([6,6]-phenyl C61-butyric acid methyl ester) mixture, without anode buffer layer, such as PEDOT:PSS layer. The metallic electrode was formed by thermally evaporated Al. Before the coating of organic layers, ITO surface was exposed to plasma made of $CF_4$ and $O_2$ gas, with/without heat treatment. In order to identify the effect the surface treatment, the current density and voltage characteristics were measured by solar simulator and the chemical composition of plasma treated ITO surface was analyzed by using X-ray photoelectron spectroscopy(XPS). In addition, the work function of the plasma treated ITO surface was measured by using ultraviolet photoelectron spectroscopy(UPS). The effects of plasma surface treatment can be attributed to the removal organic contaminants of the ITO surface, to the improvement of contact between ITO and buffer layer, and to the increase of work function of the ITO.

• Korean Journal of Materials Research
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• v.30 no.10
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• pp.566-572
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• 2020

In the recent years, thin film solar cells (TFSCs) have emerged as a viable replacement for crystalline silicon solar cells and offer a variety of choices, particularly in terms of synthesis processes and substrates (rigid or flexible, metal or insulator). Among the thin-film absorber materials, SnS has great potential for the manufacturing of low-cost TFSCs due to its suitable optical and electrical properties, non-toxic nature, and earth abundancy. However, the efficiency of SnS-based solar cells is found to be in the range of 1 ~ 4 % and remains far below those of CdTe-, CIGS-, and CZTSSe-based TFSCs. Aside from the improvement in the physical properties of absorber layer, enormous efforts have been focused on the development of suitable buffer layer for SnS-based solar cells. Herein, we investigate the device performance of SnS-based TFSCs by introducing double buffer layers, in which CdS is applied as first buffer layer and ZnMgO films is employed as second buffer layer. The effect of the composition ratio (Mg/(Mg+Zn)) of RF sputtered ZnMgO films on the device performance is studied. The structural and optical properties of ZnMgO films with various Mg/(Mg+Zn) ratios are also analyzed systemically. The fabricated SnS-based TFSCs with device structure of SLG/Mo/SnS/CdS/ZnMgO/AZO/Al exhibit a highest cell efficiency of 1.84 % along with open-circuit voltage of 0.302 V, short-circuit current density of 13.55 mA cm^-2, and fill factor of 0.45 with an optimum Mg/(Mg + Zn) ratio of 0.02.

• Korean Journal of Materials Research
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• v.28 no.4
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• pp.235-240
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• 2018

We propose a speedy two-step deposit process to form an Au electrode on hole transport layer(HTL) without any damage using a general thermal evaporator in a perovskite solar cell(PSC). An Au electrode with a thickness of 70 nm was prepared with one-step and two-step processes using a general thermal evaporator with a 30 cm source-substrate distance and $6.0{\times}10^{-6}$ torr vacuum. The one-step process deposits the Au film with the desirable thickness through a source power of 60 and 100 W at a time. The two-step process deposits a 7 nm-thick buffer layer with source power of 60, 70, and 80 W, and then deposits the remaining film thickness at higher source power of 80, 90, and 100 W. The photovoltaic properties and microstructure of these PSC devices with a glass/FTO/$TiO_2$/perovskite/HTL/Au electrode were measured by a solar simulator and field emission scanning electron microscope. The one-step process showed a low depo-temperature of $88.5^{\circ}C$ with a long deposition time of 90 minutes at 60 W. It showed a high depo-temperature of $135.4^{\circ}C$ with a short deposition time of 8 minutes at 100 W. All the samples showed an ECE lower than 2.8 % due to damage on the HTL. The two-step process offered an ECE higher than 6.25 % without HTL damage through a deposition temperature lower than $88^{\circ}C$ and a short deposition time within 20 minutes in general. Therefore, the proposed two-step process is favorable to produce an Au electrode layer for the PSC device with a general thermal evaporator.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.10
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• pp.648-651
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• 2015

The characterizations of zinc oxide (ZnO) buffer layers grown by unbalanced magnetron (UBM) sputtering under various substrate temperatures for inverted organic solar cells (IOSCs) were investigated. UBM sputter grown ZnO films exhibited higher crystallinity with increasing the substrate temperature, resulting in uniform and large grain size. Also, the electrical properties of ZnO films are improved with increasing substrate temperature. In the results, the performance of IOSCs critically depended on the substrate temperature during the film growth because the crystalllinity of the ZnO film affect the carrier mobility of the ZnO film.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.1
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• pp.36-41
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• 2023

We investigated the properties of vanadium oxide (VOx) buffer layers deposited by a dual RF magnetron sputtering method under various target powers for inverted organic solar cells (IOSCs). Sputter fabricatged VOx thin films exhibited higher crystallinity with the increase of target power, resulting in a uniform and large grain size. The electrical properties of VOx films are improved with the increase of target power because of the increase of V content. In the results, the performance of IOSCs critically depended on the target power during the film growth because the crystalllinity of the VOx film affects the carrier mobility of the VOx film.

• Current Photovoltaic Research
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• v.3 no.2
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• pp.54-60
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• 2015

ZnSnO thin films were deposited by atomic layer deposition (ALD) process using diethyl zinc ($Zn(C_2H_5)_2$) and tetrakis (dimethylamino) tin ($Sn(C_2H_6N)_4$) as metal precursors and water vapor as a reactant. ALD process has several advantages over other deposition methods such as precise thickness control, good conformality, and good uniformity for large area. The composition of ZnSnO thin films was controlled by varying the ratio of ZnO and $SnO_2$ ALD cycles. The ALD ZnSnO film was an amorphous state. The band gap of ZnSnO thin films increased as the Sn content increased. The CIGS solar cell using ZnSnO buffer layer showed about 18% energy conversion efficiency. With such a high efficiency with the ALD ZnSnO buffer and no light soaking effect, AlD ZnSnO buffer mighty be a good candidate to replace Zn(S,O) buffer in CIGSsolar cells.

• Journal of the Korean Physical Society
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• v.73 no.11
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• pp.1794-1798
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• 2018

We have grown famatinite $Cu_3SbS_4$ films by using sulfurization of Cu/Sb stack film. Sulfurization at $500^{\circ}C$ produced famatinite $Cu_3SbS_4$ phase, while $400^{\circ}C$ and $450^{\circ}C$ sulfurization exhibited unreacted and mixed phases. The fabricated $Cu_3SbS_4$ film showed S-deficiency, and secondary phase of $Cu_{12}Sb_4S_{13}$. The secondary phase was confirmed by X-ray diffraction, Raman spectroscopy, photoluminescence and external quantum efficiency measurements. We have also fabricated solar cell in substrate type structure, ITO/ZnO/(Zn,Sn)O/$Cu_3SbS_4$/Mo/glass, where $Cu_3SbS_4$ was used as a absorber layer and (Zn,Sn)O was employed as a Cd-free buffer. Our best cell showed power conversion efficiency of 0.198%. Characterization results of $Cu_3SbS_4$ absorber indicates deep defect (due to S-deficiency) and low shunt resistance (due to $Cu_{12}Sb_4S_{13}$ phase). Thus in order to improve the cell efficiency, it is required to grow high quality $Cu_3SbS_4$ film with no S-deficiency and no secondary phase.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.2
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• pp.121-125
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• 2014

In this research, nanocomposite layers consisting of poly (3,4,-ethylene dioxythiophene):polystyrene sulfonic acid (PEDOT:PSS) and CuO nanoparticles were investigated as hole transport layers in organic solar cells based on poly (3-hexylthiophene) (P3HT) as the electron donor and (6.6) phenyl-C61-butyric acid methyl ester (PCBM) as the electron acceptor. The addition of CuO nanoparticles to PEDOT:PSS layer improved the solar cell performance with 0.5% CuO nanoparticle concentration. At optimized concentration, CuO mixed PEDOT:PSS films had good electrical ($4.131{\Omega}{\cdot}cm$) and optical (transmittance > 90%) properties for using hole transporting layer. We investigated that improved solar cell performance with CuO nanoparticles mixed PEDOT:PSS films.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.386-386
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• 2009

TCO/p/i/n 구조의 비정질 실리콘 박막 태양전지의 제작에 있어서 TCO계면과 p층사이의 이종접합에서의 큰 밴드갭 차이는 p층으로부터의 정공 재결합을 통하여 효율 저하의 원인이 된다. 이러한 재결합은 넓은 밴드갭을 가진 물질을 완충층으로 삽입함으로써 개선되어 질 수 있다. 본 논문에서는 비정질 실리콘 보다 넓은 광학적 밴드갭을 가지는 a-SiOx 박막을 완충층으로 사용하여 TCO/P 계면에서의 재결합 감소에 대한 시뮬레이션을 수행하였다. a-SiOX 박막 내에 포함된 산소의 양에 따라 밴드갭을 조절하여 1.8eV~2.0eV 사이의 완충층을 삽입하여 박막태양전지의 개방전압, 단락전류, 효율 등에 끼치는 영향을 ASA 시뮬레이션을 통하여 알아보았다.