• Rapid Communication in Photoscience
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• v.4 no.4
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• pp.82-85
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• 2015

Photoelectrochemical cell (PEC) is one of the attractive ways to produce clean and renewable energy. However, solar to hydrogen production via PEC system generally requires high external bias, because of material's innate electronic band potential relative to hydrogen reduction potential and/or charge separation issue. For spontaneous photo-water splitting, here, we design dye-sensitized solar cell (DSSC) and their monolithic tandem cell incorporated with a $BiVO_4$ photoanode. $BiVO_4$ has high conduction band edge potential and suitable band gap (2.4eV) to absorb visible light. To achieve efficient $BiVO_4$ photoanode system, electron and hole mobility should be improved, and we demonstrate a tandem cell in which $BiVO_4/WO_3$ film is connected to cobalt complex based DSSC.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.5
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• pp.442-453
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• 2023

Tandem or multijunction solar cells (MJSCs) can convert sunlight into electricity with higher efficiency (η) than single junction solar cells (SJSCs) by dividing the solar irradiance over sub-cells having distinct bandgaps. The efficiencies of various common SJSC materials are close to the edge of their theoretical efficiency and hence there is a tremendous growing interest in utilizing the tandem/multijunction technique. Recently, III-V materials integration on a silicon substrate has been broadly investigated in the development of III-V on Si tandem solar cells. Numerous growth techniques such as heteroepitaxial growth, wafer bonding, and mechanical stacking are crucial for better understanding of high-quality III-V epitaxial layers on Si. As the choice of growth method and substrate selection can significantly impact the quality and performance of the resulting tandem cell and the terminal configuration exhibit a vital role in the overall proficiency. Parallel and Series-connected configurations have been studied, each with its advantage and disadvantages depending on the application and cell configuration. The optimization of both growth mechanisms and terminal configurations is necessary to further improve efficiency and lessen the cost of III-V on Si tandem solar cells. In this review article, we present an overview of the growth mechanisms and terminal configurations with the areas of research that are crucial for the commercialization of III-V on Si tandem solar cells.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.257.2-257.2
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• 2015

In this paper, we report on the 10.33% efficient thin film/bulk tandem solar cells with the top cell made of amorphous silicon thin film and p-type bulk crystalline silicon bottom cell. The tunneling junction layers were used the doped nanocrystalline Si layers. It has to allow an ohmic and low resistive connection. For player and n-layer, crystalline volume fraction is ~86%, ~88% and dark conductivity is $3.28{\times}10-2S/cm$, $3.03{\times}10-1S/cm$, respectively. Optimization of the tunneling junction results in fill factor of 66.16 % and open circuit voltage of 1.39 V. The open circuit voltage was closed to the sum of those of the sub-cells. This tandem structure could enable the effective development of a new concept of high-efficiency and low cost cells.

• JSTS:Journal of Semiconductor Technology and Science
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• v.9 no.2
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• pp.91-97
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• 2009

The performance of GaInP/GaAs tandem solar cells with AlInP growth temperatures of 680$^{\circ}C$ and 700 $^{\circ}C$ on n-type GaAs (100) substrate with 2$^{\circ}$ and 6$^{\circ}$ tilt angles has been investigated. The series resistance and open circuit voltage of the fabricated tandem solar cells are affected by the substrate tilt angles and the growth temperatures of the window layer when zinc is doped in the tunnel diode. With carbon doping as a p-type doping source in the tunnel diode and the effort of current matching between top and bottom cells, GaInP/GaAs tandem solar cell has been exhibited 25.58% efficiency.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.318-318
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• 2010

We present the effect of interlayers of polymer tandem solar cells on their photovoltaic performance. P-type and n-type interlayers are essential for the series-connection of the subcells and enable to form the tandem cell architecture by the solution processing. In this study, we use PEDOT:PSS, nanocrystalline $TiO_2$, and blends of semiconducting polymers and fullerene derivatives as a hole transporting layer, electron transporting layer, and photoactive layers, respectively. We show that photovoltaic performances of polymer tandem solar cells depending on various PEDOT:PSS layers with the different electric conductivity and the various $TiO_2$ layer thickness.

• Solar Energy
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• v.18 no.3
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• pp.137-146
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• 1998

In this paper, the current status of manufacturing technologies for GaAs/Si solar cell were revived and provied new MOCVD. In the manufacturing process of GaAs/Si solar cells and an experiment to get the high efficiency GaAs solar cells, we must investigate the optimum growth conditions to get high quality GaAs films on Si substrates by MOCVD. The GaAs on Si substrates has been recognized as a lightweight alternative to pure substrate for space applicaton. Because its density is less the half of GaAs or Ge.So GaAs/Si has twofold weight advantage to GaAs monolithic cell. The theoretical conversion efficiecy limit of tandem GaAs/Si solar cell is 32% under AM 0 and $25^{\circ}C$ condition. It was concluded that the development of cost effective MOCVD technologies shoud be ahead GaAs solar cells for achived move high efficiency III-V solar cells involving tandem structure.

• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.228-231
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• 2006

This paper briefly introduces silicon based thin film solar cells: amorphous (a-Si:H), microcrystalline ${\mu}c-Si:H$ single junction and $a-Si:H/{\mu}c-Si:H$ tandem solar cells. The major difference of a-Si:H and ${\mu}c-Si:H$ cells comes from electro-optical properties of intrinsic Si-films (active layer) that absorb incident photon and generate electron-hole pairs. The a-Si:H film has energy band-gap (Eg) of 1.7-1.8eV and solar cells incorporating this wide Eg a-Si:H material as active layer commonly give high voltage and low current, when illuminated, compared to ${\mu}c-Si:H$ solar cells that employ low Eg (1.1eV) material. This Eg difference of two materials make possible tandem configuration in order to effectively use incident photon energy. The $a-Si:H/{\mu}c-Si:H$ tandem solar cells, therefore, have a great potential for low cost photovoltaic device by its various advantages such as low material cost by thin-film structure on low cost substrate instead of expensive c-Si wafer and high conversion efficiency by tandem structure. In this paper, the structure, process and operation properties of Si-based thin-film solar cells are discussed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.452-453
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• 2008

pin 두 개의 층으로 이루어진 적층형 박막 태양전지를 이용하여 시뮬레이션 하였다. 각 층별 두께를 조절하여 층별 효율을 측정 하였다. 또한 각 층의 도핑 농도를 조절하여 층별 효율을 측정하였다. 그 후 각각 두 개의 층의 최대효율을 측정하였고 동일한 값으로 두 층이 직렬 연결된 태양전지의 효율을 측정하였다. 그 결과 최대 10.14%로 측정 되었다.

• Current Photovoltaic Research
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• v.8 no.1
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• pp.6-11
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• 2020

The power conversion efficiency (PCE) of a two-terminal tandem solar cell depends upon the tunnel-recombination junction (TRJ) between the top and bottom sub-cells. An optimized TRJ in a tandem cell helps improve its open-circuit voltage (V_oc), short-circuit current density (J_sc), fill factor (FF), and efficiency (PCE). One of the parameters that affect the TRJ is the buffer layer thickness. Therefore, we investigated various TRJs by varying the thickness of the buffer or intermediate layer (TRJ-buffer) in between the highly doped p-type and n-type layers of the TRJ. The TRJ-buffer layer was p-type nc-Si:H, with a doping of 0.06%, an activation energy (E_a) of 43 meV, an optical gap (E_g) of 2.04 eV, and its thickness was varied from 0 nm to 125 nm. The tandem solar cells we investigated were a combination of a heterojunction with intrinsic thin layer (HIT) bottom sub-cell and an a-Si:H (amorphous silicon) top sub-cell. The initial cell efficiency without the TRJ buffer was 7.65% while with an optimized buffer layer, its efficiency improved to 11.74%, i.e., an improvement in efficiency by a factor of 1.53.

• 한국신재생에너지학회:학술대회논문집
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• 2008.10a
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• pp.131-133
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• 2008

A serious problem of the 21st century is the supply of energy resources. Reserves of fossil fuels are facing depletion: renewable energy resources must be developed in this era. Dye sensitized solar cell (DSC) has been very economical and easy method to convert solar energy to electricity. Recently a novel tandem cell structure is proposed to improve photocurrent of DSC. To fabricated a tandem cell, the mesh structure of counter electrode is essential for the improvement in transmittance. In this study, we conducted the experiment to get the characteristic of DSC with mesh counter electrode. Under the standard test condition (AM 1.5, 100mW/$cm^2$), we obtained the maximum efficiency of 3.41% and the transmittance of 72% in the DSC with mesh counter electrode.