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Author

Kyungsun Ryu

Other affiliations: Columbia University
Bio: Kyungsun Ryu is an academic researcher from Georgia Institute of Technology. The author has contributed to research in topics: Common emitter & Boron. The author has an hindex of 10, co-authored 23 publications receiving 302 citations. Previous affiliations of Kyungsun Ryu include Columbia University.

Papers
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Journal ArticleDOI
TL;DR: In this paper, an effective chemical etching treatment to remove a boron-rich layer which has a significant negative impact on n-type silicon (Si) solar cells with a BORON emitter was reported.
Abstract: This paper reports on an effective chemical etching treatment to remove a boron-rich layer which has a significant negative impact on n-type silicon (Si) solar cells with boron emitter. A nitric acid-grown oxide/silicon nitride stack passivation on the boron-rich layer-etched boron emitter markedly decreases the emitter saturation current density J0e from 430 to 100 fA/cm2. This led to 1.6% increase in absolute cell efficiency including 22 mV increase in open-circuit voltage Voc and 1.9 mA/cm2 increase in short-circuit current density Jsc. This resulted in screen-printed large area (239 cm2) n-type Si solar cells with efficiency of 19.0%.

49 citations

Journal ArticleDOI
TL;DR: In this paper, the detailed optical properties of various SiN films and their effect on silicon solar cell efficiency in air and under glass is evaluated by a combination of Monte-Carlo geometrical ray tracing program, Sunrays, and a device modeling program PC1D.
Abstract: Plasma-enhanced chemical vapor deposition (PECVD) SiN films are widely used as antireflection (AR) coating for silicon solar cells and particularly for multi-crystalline solar cells for hydrogen passivation of bulk defects. In this paper, the detailed optical properties of various SiN films and their effect on silicon solar cell efficiency in air and under glass is evaluated by a combination of Monte-Carlo geometrical ray tracing program, Sunrays, and a device modeling program PC1D. Maximum module power under glass and ethylene vinyl acetate (EVA) encapsulation is used as the figure of merit for optimizing the index and thickness of the SiN films. Simulations are categorized by surface morphology (planar or textured) and ambient (air or glass). SiN films with refractive index (n) in the range of 2.03–2.42 are used for this study. It is found that although n = 2.03 is not the optimum index in terms of reflectance under glass (n = 1.5), it produces maximum cell or module efficiency under glass. This is because n = 2.03 film produces much higher cell efficiency (17.9%) in air, therefore, even after a significant optical encapsulation loss of 0.8% in absolute efficiency, the cell efficiency remains highest (17.1%) under glass. In contrast SiN film with an index of 2.4 produces only 0.5% air to glass efficiency loss but due to the low starting efficiency of 17% in air; the final cell efficiency under glass is only 16.5%. In addition, texturing provides a larger window of thickness around the optimum without affecting the optical performance. Similar analysis done for planar cells indicate that optimum index for highest module power is 2.20. This is because reflection is much higher in planar cells, therefore higher index can be tolerated before loss due to absorption in SiN exceeds the gain in reflectance under glass. Copyright © 2011 John Wiley & Sons, Ltd.

48 citations

Journal ArticleDOI
TL;DR: In this article, the fabrication of front junction n-type Si solar cells on 239 cm 2 Cz using ion implanted boron emitter and phosphorus back surface field (BSF) in combination with screen printed metallization was reported.

43 citations

Journal ArticleDOI
TL;DR: In this article, a thin thermal-SiO2/SiNX stack was demonstrated to provide similar passivation on both p+ and n+ surfaces, and a spin-on boric acid source was used to create uniform, well-passivated p+ emitters on textured surfaces.
Abstract: N-type Si cells offer a compelling alternative to p-type cells to achieve high, stabilized cell efficiencies because they do not suffer from light-induced degradation. However, the most common dielectric materials that are used to passivate the n+ emitters of p-type cells-thermal SiO2 and SiNX-have historically provided poor passivation of the p+ emitters required for n-type cells. In this paper, we demonstrate that a thin thermal-SiO2/SiNX stack can, when appropriately fired, provide similar passivation on both p+ and n+ surfaces. Passivation studies on textured, SiO2/SiNX passivated p+-Si surfaces indicate that a high-temperature firing cycle is the most important step to achieving high-quality passivation and that the positive charge in the dielectric stack may have little detrimental effect on industrial-type, high surface concentration emitters. In addition, the suitability of spin-on boric acid sources for forming uniform, well-passivated p+ emitters on textured surfaces was studied. This passivation scheme and spin-on boron source were used to achieve 4-cm2 screen-printed n-type cells with efficiencies over 20% and open-circuit voltages up to 650 mV.

31 citations

Proceedings ArticleDOI
19 Jun 2011
TL;DR: In this article, a thermal SiO 2 and SiN x stack was used to passivate planar and textured boron diffused surfaces of n-type solar cells.
Abstract: Due partly to the fact that n-type solar cells do not suffer from light-induced degradation, there has been a recent surge in research and industrial interest in n-type silicon solar cells. However, the most common dielectric materials that are used to passivate the surface of p-type cells — thermal oxide and silicon nitride — are well known to have problems with providing adequate passivation of heavily boron doped surfaces, especially on textured surfaces. As a result, the highest efficiency n-type cells have thus far relied on Al 2 O 3 whose high negative charge density results in good passivation on both planar and textured boron diffused surfaces. We show here that though thermal SiO 2 and SiN x alone provide poor passivation on p+ surfaces, a thin (15 nm) thermal-SiO 2 layer, capped with SiN x can, after firing, provide high-quality passivation on a textured, boron emitter. Firing at ∼ 750°C was found to result in a threefold improvement in the surface passivation quality with a final J 0 of ∼ 150 fA/cm2 being achieved. Additionally, a spin-on boric acid source was used to form a uniform, textured emitter as verified on completed solar cells which did not demonstrate junction shunting. Using a symmetric SiO 2 /SiN x stack passivation and screen-printed contacts, a verified n-type cell efficiency of 20.3% was achieved with V OC up to 650mV and J SC over 40mA/cm2. The stability of this structure was also tested, with no degradation being observed over 7 months of dark storage in air.

29 citations


Cited by
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Journal ArticleDOI
TL;DR: In this paper, a donor-acceptor based solution processable low band gap polymer semiconductor, PDPP-TNT, was synthesized via Suzuki coupling using condensed diketopyrrolopyrrole (DPP) as an acceptor moiety with a fused naphthalene donor building block in the polymer backbone.
Abstract: In this work, we report a novel donor–acceptor based solution processable low band gap polymer semiconductor, PDPP–TNT, synthesized via Suzuki coupling using condensed diketopyrrolopyrrole (DPP) as an acceptor moiety with a fused naphthalene donor building block in the polymer backbone. This polymer exhibits p-channel charge transport characteristics when used as the active semiconductor in organic thin-film transistor (OTFT) devices. The hole mobilities of 0.65 cm2 V−1s−1 and 0.98 cm2 V−1s−1 are achieved respectively in bottom gate and dual gate OTFT devices with on/off ratios in the range of 105 to 107. Additionally, due to its appropriate HOMO (5.29 eV) energy level and optimum optical band gap (1.50 eV), PDPP–TNT is a promising candidate for organic photovoltaic (OPV) applications. When this polymer semiconductor is used as a donor and PC71BM as an acceptor in OPV devices, high power conversion efficiencies (PCE) of 4.7% are obtained. Such high mobility values in OTFTs and high PCE in OPV make PDPP–TNT a very promising polymer semiconductor for a wide range of applications in organic electronics.

178 citations

Journal ArticleDOI
TL;DR: In this paper, strategies for the utilization of dewetting of polymer thin film to fabricate ordered patterns are reviewed, and simulation results of pattern formation induced by physically and chemically patterned substrates, and physical confinement are summarized.

145 citations

Journal ArticleDOI
TL;DR: In the past few decades, the fabrication of solar cells has been considered as one of the most promising ways to meet the increasing energy demands to support the development of modern society as well as to control the environmental pollution caused by the combustion of fossil fuels as discussed by the authors.
Abstract: In the past few decades, the fabrication of solar cells has been considered as one of the most promising ways to meet the increasing energy demands to support the development of modern society as well as to control the environmental pollution caused by the combustion of fossil fuels. A number of different types of solar cells, such as silicon solar cells (Si), Cu-based chalcogenides (Cu(In,Ga)Se2/Cu2ZnSn(S,Se)4) thin film solar cells (TFSC), dye-sensitized solar cells (DSSC), organic solar cells (OSC), and perovskite solar cells (PVSC), have been implemented in the photovoltaic technology. However, the high manufacturing costs of solar cells is one of the major obstacles for their wide-scale application. In this regard, inkjet printing has attracted tremendous interest in both academic research and industrial applications among all the various kinds of fabrication techniques and is believed to be one of the most promising methods to meet these requirements. The great advantages of inkjet printing are that the process is contactless, maskless and has a high material utilization rate, and good scalability, and compatibility of the roll-to-roll process. Additionally, the maskless nature of inkjet printing allows for freedom of design, which enables multi-functional properties of solar cells (i.e., power source and artwork) to be realized. In this review, the recent advances in inkjet printing with the deposition of different layers of various types of solar cells are summarized in detail and prospectives for the future development of printed/flexible solar cells are covered.

87 citations

Journal ArticleDOI
TL;DR: In this article, a carrier-selective tunnel oxide passivated rear contact for high-efficiency screen-printed large area n-type front junction crystalline Si solar cells was proposed.
Abstract: This paper reports on the implementation of carrier-selective tunnel oxide passivated rear contact for high-efficiency screen-printed large area n-type front junction crystalline Si solar cells. It is shown that the tunnel oxide grown in nitric acid at room temperature (25°C) and capped with n+ polysilicon layer provides excellent rear contact passivation with implied open-circuit voltage iVoc of 714 mV and saturation current density J0b′ of 10.3 fA/cm2 for the back surface field region. The durability of this passivation scheme is also investigated for a back-end high temperature process. In combination with an ion-implanted Al2O3-passivated boron emitter and screen-printed front metal grids, this passivated rear contact enabled 21.2% efficient front junction Si solar cells on 239 cm2 commercial grade n-type Czochralski wafers. Copyright © 2016 John Wiley & Sons, Ltd.

83 citations

Journal ArticleDOI
TL;DR: In this paper, the rapid progress in the development of inorganic and organic solar cells (SCs) such as silicon, perovskite, III-V, quantum dot, dye sensitized, flexible SCs, thin film SCs and tandem SCs are reviewed.

78 citations