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Kostya Ostrikov - One of the best experts on this subject based on the ideXlab platform.
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si quantum dots embedded in an amorphous sic matrix nanophase control by non equilibrium plasma Hydrogenation
Science & Engineering Faculty, 2010Co-Authors: Qijin Cheng, Eugene Tam, Kostya OstrikovAbstract:Nanophase nc-Si/a-SiC films that contain Si quantum dots (QDs) embedded in an amorphous SiC matrix were deposited on single-crystal silicon substrates using inductively coupled plasma-assisted chemical vapor deposition from the reactive silane and methane precursor gases diluted with Hydrogen at a substrate temperature of 200 °C. The effect of the Hydrogen Dilution ratio X (X is defined as the flow rate ratio of Hydrogen-to-silane plus methane gases), ranging from 0 to 10.0, on the morphological, structural, and compositional properties of the deposited films, is extensively and systematically studied by scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, Raman spectroscopy, Fourier-transform infrared absorption spectroscopy, and X-ray photoelectron spectroscopy. Effective nanophase segregation at a low Hydrogen Dilution ratio of 4.0 leads to the formation of highly uniform Si QDs embedded in the amorphous SiC matrix. It is also shown that with the increase of X, the crystallinity degree and the crystallite size increase while the carbon content and the growth rate decrease. The obtained experimental results are explained in terms of the effect of Hydrogen Dilution on the nucleation and growth processes of the Si QDs in the high-density plasmas. These results are highly relevant to the development of next-generation photovoltaic solar cells, light-emitting diodes, thin-film transistors, and other applications.
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single step rapid low temperature synthesis of si quantum dots embedded in an amorphous sic matrix in high density reactive plasmas
Acta Materialia, 2010Co-Authors: Qijin Cheng, Shuyan Xu, Kostya OstrikovAbstract:Abstract A simple, effective and innovative approach based on low-pressure, thermally nonequilibrium, high-density inductively coupled plasmas is proposed to rapidly synthesize Si quantum dots (QDs) embedded in an amorphous SiC ( a -SiC) matrix at a low substrate temperature and without any commonly used Hydrogen Dilution. The experimental results clearly demonstrate that uniform crystalline Si QDs with a size of 3–4 nm embedded in the silicon-rich (carbon content up to 10.7at.%) a -SiC matrix can be formed from the reactive mixture of silane and methane gases, with high growth rates of ∼1.27–2.34 nm s −1 and at a low substrate temperature of 200 °C. The achievement of the high-rate growth of Si QDs embedded in the a -SiC without any commonly used Hydrogen Dilution is discussed based on the unique properties of the inductively coupled plasma-based process. This work is particularly important for the development of the all-Si tandem cell-based third generation photovoltaic solar cells.
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rapid low temperature synthesis of nc si in high density non equilibrium plasmas enabling nanocrystallinity at very low Hydrogen Dilution
Journal of Materials Chemistry, 2009Co-Authors: Qijin Cheng, Shuyan Xu, Kostya OstrikovAbstract:Nanocrystalline silicon thin films were deposited on single-crystal silicon and glass substrates simultaneously by inductively coupled plasma-assisted chemical vapor deposition from the reactive silane reactant gas diluted with Hydrogen at a substrate temperature of 200 °C. The effect of Hydrogen Dilution ratio X (X is defined as the flow rate ratio of Hydrogen to silane gas), ranging from 1 to 20, on the structural and optical properties of the deposited films, is extensively investigated by Raman spectroscopy, X-ray diffraction, Fourier transform infrared absorption spectroscopy, UV/VIS spectroscopy, and scanning electron microscopy. Our experimental results reveal that, with the increase of the Hydrogen Dilution ratio X, the deposition rate Rd and Hydrogen content CH are reduced while the crystalline fraction Fc, mean grain size δ and optical bandgap ETauc are increased. In comparison with other plasma enhanced chemical vapor deposition methods of nanocrystalline silicon films where a very high Hydrogen Dilution ratio X is routinely required (e.g. X > 16), we have achieved nanocrystalline silicon films at a very low Hydrogen Dilution ratio of 1, featuring a high deposition rate of 1.57 nm/s, a high crystalline fraction of 67.1%, a very low Hydrogen content of 4.4 at.%, an optical bandgap of 1.89 eV, and an almost vertically aligned columnar structure with a mean grain size of approximately 19 nm. We have also shown that a sufficient amount of atomic Hydrogen on the growth surface essential for the formation of nanocrystalline silicon is obtained through highly-effective dissociation of silane and Hydrogen molecules in the high-density inductively coupled plasmas.
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structural evolution of nanocrystalline silicon thin films synthesized in high density low temperature reactive plasmas
Nanotechnology, 2009Co-Authors: Qijin Cheng, Kostya OstrikovAbstract:Silicon thin films with a variable content of nanocrystalline phase were deposited on single-crystal silicon and glass substrates by inductively coupled plasma-assisted chemical vapor deposition using a silane precursor without any Hydrogen Dilution in the low substrate temperature range from 100 to 300 degrees C. The structural and optical properties of the deposited films are systematically investigated by Raman spectroscopy, x-ray diffraction, Fourier transform infrared absorption spectroscopy, UV/vis spectroscopy, scanning electron microscopy and high-resolution transmission electron microscopy. It is shown that the structure of the silicon thin films evolves from the purely amorphous phase to the nanocrystalline phase when the substrate temperature is increased from 100 to 150 degrees C. It is found that the variations of the crystalline fraction f(c), bonded Hydrogen content C(H), optical bandgap E(Tauc), film microstructure and growth rate R(d) are closely related to the substrate temperature. In particular, at a substrate temperature of 300 degrees C, the nanocrystalline Si thin films of our interest feature a high growth rate of 1.63 nm s(-1), a low Hydrogen content of 4.0 at.%, a high crystalline fraction of 69.1%, a low optical bandgap of 1.55 eV and an almost vertically aligned columnar structure with a mean grain size of approximately 10 nm. It is also shown that the low-temperature synthesis of nanocrystalline Si thin films without any Hydrogen Dilution is attributed to the outstanding dissociation ability of the high-density inductively coupled plasmas and effective plasma-surface interactions during the growth process. Our results offer a highly effective yet simple and environmentally friendly technique to synthesize high-quality nanocrystalline Si films, vitally needed for the development of new-generation solar cells and other emerging nanotechnologies.
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rapid low temperature synthesis of nc si in high density non equilibrium plasmas enabling nanocrystallinity at very low Hydrogen Dilution
Science & Engineering Faculty, 2009Co-Authors: Qijin Cheng, Shuyan Xu, Kostya OstrikovAbstract:Nanocrystalline silicon thin films were deposited on single-crystal silicon and glass substrates simultaneously by inductively coupled plasma-assisted chemical vapor deposition from the reactive silane reactant gas diluted with Hydrogen at a substrate temperature of 200 °C. The effect of Hydrogen Dilution ratio X (X is defined as the flow rate ratio of Hydrogen to silane gas), ranging from 1 to 20, on the structural and optical properties of the deposited films, is extensively investigated by Raman spectroscopy, X-ray diffraction, Fourier transform infrared absorption spectroscopy, UV/VIS spectroscopy, and scanning electron microscopy. Our experimental results reveal that, with the increase of the Hydrogen Dilution ratio X, the deposition rate Rd and Hydrogen content CH are reduced while the crystalline fraction Fc, mean grain size δ and optical bandgap ETauc are increased. In comparison with other plasma enhanced chemical vapor deposition methods of nanocrystalline silicon films where a very high Hydrogen Dilution ratio X is routinely required (e.g. X > 16), we have achieved nanocrystalline silicon films at a very low Hydrogen Dilution ratio of 1, featuring a high deposition rate of 1.57 nm/s, a high crystalline fraction of 67.1%, a very low Hydrogen content of 4.4 at.%, an optical bandgap of 1.89 eV, and an almost vertically aligned columnar structure with a mean grain size of approximately 19 nm. We have also shown that a sufficient amount of atomic Hydrogen on the growth surface essential for the formation of nanocrystalline silicon is obtained through highly-effective dissociation of silane and Hydrogen molecules in the high-density inductively coupled plasmas. © 2009 The Royal Society of Chemistry.
Makoto Konagai - One of the best experts on this subject based on the ideXlab platform.
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fabrication of a sigec h solar cells using monomethyl germane by suppressing carbon incorporation for narrowing optical bandgap
Solar Energy Materials and Solar Cells, 2011Co-Authors: Do Yun Kim, Ihsanul Afdi Yunaz, Shinsuke Miyajima, Shunsuke Kasashima, Makoto KonagaiAbstract:Abstract Hydrogenated amorphous silicon–germanium–carbide (a-SiGeC:H) thin films have been fabricated by very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD) using monomethyl germane (MMG, GeH 3 CH 3 ) as the germanium source. It was found that C incorporation into the films was considerably suppressed under high Hydrogen Dilution ( R H ) and substrate temperature ( T S ). Under high R H and T S , we were able to narrow the optical band gap ( E opt ) of a-SiGeC:H thin films to 1.39 eV, whereas under low R H and T S , E opt increased up to 1.9 eV with increasing MMG. The best electrical properties were obtained for a sample of a-Si 0.68 Ge 0.29 C 0.03 :H, whose E opt and photosensitivity were 1.58 eV and 10 5 , respectively. When this film was used as an absorber layer in a p–i–n structured solar cell, significant enhancements were observed in its quantum efficiency for long wavelengths.
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Hydrogenated amorphous silicon oxide solar cells fabricated near the phase transition between amorphous and microcrystalline structures
Japanese Journal of Applied Physics, 2009Co-Authors: Sorapong Inthisang, Shinsuke Miyajima, Akira Yamada, Kobsak Sriprapha, Makoto KonagaiAbstract:We investigated the properties of Hydrogenated amorphous silicon oxide (a-Si1-xOx:H) deposited near the phase transition between amorphous and microcrystalline structures. a-Si1-xOx:H films were prepared by plasma-enhanced chemical vapor deposition using a gas mixture of silane, Hydrogen, and carbon dioxide. The film structure was changed from amorphous to microcrystalline phase by increasing Hydrogen Dilution. Optical and electrical characterizations revealed that wide-gap a-Si1-xOx:H films were deposited under phase transition conditions. We also fabricated a-Si1-xOx:H single-junction p–i–n solar cells by varying the Hydrogen Dilution for the i-layer. The solar cells showed a maximum open circuit voltage of 1.04 V (Jsc=7.92 mA/cm2, FF=0.64, Eff=5.2%) when the i-layer was deposited under phase transition conditions.
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fabrication of amorphous silicon carbide films using vhf pecvd for triple junction thin film solar cell applications
Solar Energy Materials and Solar Cells, 2009Co-Authors: Ihsanul Afdi Yunaz, Shinsuke Miyajima, Akira Yamada, Kenji Hashizume, Makoto KonagaiAbstract:Abstract Preparation of intrinsic Hydrogenated amorphous silicon carbide (i-a-SiC:H) thin films for use as a top cell of triple junction solar cells is presented. These films were deposited using very-high-frequency plasma-enhanced chemical vapor deposition (VHF-PECVD) technique with monomethyl silane (MMS) gas as the carbon source. Deposition conditions were explored to obtain films with a wide gap and low defect density. It was confirmed that the Hydrogen Dilution ratio plays an important role in enhancing the film properties. Employing a-SiC:H film as an intrinsic layer of single junction cell, open-circuit voltage as high as 0.99 V has been achieved.
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deposition and characterization of μc ge1 xcx thin films grown by hot wire chemical vapor deposition using organo germane
Thin Solid Films, 2006Co-Authors: Yasutoshi Yashiki, Shinsuke Miyajima, Akira Yamada, Makoto KonagaiAbstract:Abstract Microcrystalline germanium carbon (μc-Ge 1− x C x ) films prepared by hot-wire chemical vapor deposition were characterized by Raman, Fourier transform infra-red and X-ray photoelectron spectroscopy. μc-Ge 1− x C x films ( x = 0.02 to 0.03 by using dimethylgermane and x = 0.07 to 0.08 by using monomethylgermane) were successfully deposited using organo-germane and Hydrogen. Raman scattering measurements reveal that the microcrystalline films could be obtained with high Hydrogen Dilution conditions. X-ray photoelectron spectroscopy measurements suggest the possible bonding of carbon with Ge atoms in the deposited thin films. The conductivity of the films were 10 − 3 ∼10 − 1 S/cm for microcrystalline films and 10 − 8 ∼10 − 5 S/cm for amorphous films. The dissociation efficiency of monomethylgermane is found to be higher than that of dimethylgermane.
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properties of Hydrogenated microcrystalline cubic silicon carbide films deposited by hot wire chemical vapor deposition at a low substrate temperature
Japanese Journal of Applied Physics, 2004Co-Authors: Shinsuke Miyajima, Akira Yamada, Makoto KonagaiAbstract:Stoichiometric Hydrogenated microcrystalline cubic silicon carbide (µc-3C-SiC:H) films were successfully deposited by hot wire chemical vapor deposition (HWCVD) at a substrate temperature of 280°C using monomethylsilane and Hydrogen. The ratio of Hydrogen to monomethylsilane (Hydrogen Dilution ratio) strongly affected the structural and electrical properties of µc-3C-SiC:H films. Subgap absorption measurements on the films revealed that the defect density of the films was influenced by Hydrogen Dilution ratio. This result indicates that Hydrogen Dilution ratio is one of the key parameters for obtaining µc-3C-SiC:H with low defect density.
Qijin Cheng - One of the best experts on this subject based on the ideXlab platform.
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si quantum dots embedded in an amorphous sic matrix nanophase control by non equilibrium plasma Hydrogenation
Science & Engineering Faculty, 2010Co-Authors: Qijin Cheng, Eugene Tam, Kostya OstrikovAbstract:Nanophase nc-Si/a-SiC films that contain Si quantum dots (QDs) embedded in an amorphous SiC matrix were deposited on single-crystal silicon substrates using inductively coupled plasma-assisted chemical vapor deposition from the reactive silane and methane precursor gases diluted with Hydrogen at a substrate temperature of 200 °C. The effect of the Hydrogen Dilution ratio X (X is defined as the flow rate ratio of Hydrogen-to-silane plus methane gases), ranging from 0 to 10.0, on the morphological, structural, and compositional properties of the deposited films, is extensively and systematically studied by scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, Raman spectroscopy, Fourier-transform infrared absorption spectroscopy, and X-ray photoelectron spectroscopy. Effective nanophase segregation at a low Hydrogen Dilution ratio of 4.0 leads to the formation of highly uniform Si QDs embedded in the amorphous SiC matrix. It is also shown that with the increase of X, the crystallinity degree and the crystallite size increase while the carbon content and the growth rate decrease. The obtained experimental results are explained in terms of the effect of Hydrogen Dilution on the nucleation and growth processes of the Si QDs in the high-density plasmas. These results are highly relevant to the development of next-generation photovoltaic solar cells, light-emitting diodes, thin-film transistors, and other applications.
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single step rapid low temperature synthesis of si quantum dots embedded in an amorphous sic matrix in high density reactive plasmas
Acta Materialia, 2010Co-Authors: Qijin Cheng, Shuyan Xu, Kostya OstrikovAbstract:Abstract A simple, effective and innovative approach based on low-pressure, thermally nonequilibrium, high-density inductively coupled plasmas is proposed to rapidly synthesize Si quantum dots (QDs) embedded in an amorphous SiC ( a -SiC) matrix at a low substrate temperature and without any commonly used Hydrogen Dilution. The experimental results clearly demonstrate that uniform crystalline Si QDs with a size of 3–4 nm embedded in the silicon-rich (carbon content up to 10.7at.%) a -SiC matrix can be formed from the reactive mixture of silane and methane gases, with high growth rates of ∼1.27–2.34 nm s −1 and at a low substrate temperature of 200 °C. The achievement of the high-rate growth of Si QDs embedded in the a -SiC without any commonly used Hydrogen Dilution is discussed based on the unique properties of the inductively coupled plasma-based process. This work is particularly important for the development of the all-Si tandem cell-based third generation photovoltaic solar cells.
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rapid low temperature synthesis of nc si in high density non equilibrium plasmas enabling nanocrystallinity at very low Hydrogen Dilution
Journal of Materials Chemistry, 2009Co-Authors: Qijin Cheng, Shuyan Xu, Kostya OstrikovAbstract:Nanocrystalline silicon thin films were deposited on single-crystal silicon and glass substrates simultaneously by inductively coupled plasma-assisted chemical vapor deposition from the reactive silane reactant gas diluted with Hydrogen at a substrate temperature of 200 °C. The effect of Hydrogen Dilution ratio X (X is defined as the flow rate ratio of Hydrogen to silane gas), ranging from 1 to 20, on the structural and optical properties of the deposited films, is extensively investigated by Raman spectroscopy, X-ray diffraction, Fourier transform infrared absorption spectroscopy, UV/VIS spectroscopy, and scanning electron microscopy. Our experimental results reveal that, with the increase of the Hydrogen Dilution ratio X, the deposition rate Rd and Hydrogen content CH are reduced while the crystalline fraction Fc, mean grain size δ and optical bandgap ETauc are increased. In comparison with other plasma enhanced chemical vapor deposition methods of nanocrystalline silicon films where a very high Hydrogen Dilution ratio X is routinely required (e.g. X > 16), we have achieved nanocrystalline silicon films at a very low Hydrogen Dilution ratio of 1, featuring a high deposition rate of 1.57 nm/s, a high crystalline fraction of 67.1%, a very low Hydrogen content of 4.4 at.%, an optical bandgap of 1.89 eV, and an almost vertically aligned columnar structure with a mean grain size of approximately 19 nm. We have also shown that a sufficient amount of atomic Hydrogen on the growth surface essential for the formation of nanocrystalline silicon is obtained through highly-effective dissociation of silane and Hydrogen molecules in the high-density inductively coupled plasmas.
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structural evolution of nanocrystalline silicon thin films synthesized in high density low temperature reactive plasmas
Nanotechnology, 2009Co-Authors: Qijin Cheng, Kostya OstrikovAbstract:Silicon thin films with a variable content of nanocrystalline phase were deposited on single-crystal silicon and glass substrates by inductively coupled plasma-assisted chemical vapor deposition using a silane precursor without any Hydrogen Dilution in the low substrate temperature range from 100 to 300 degrees C. The structural and optical properties of the deposited films are systematically investigated by Raman spectroscopy, x-ray diffraction, Fourier transform infrared absorption spectroscopy, UV/vis spectroscopy, scanning electron microscopy and high-resolution transmission electron microscopy. It is shown that the structure of the silicon thin films evolves from the purely amorphous phase to the nanocrystalline phase when the substrate temperature is increased from 100 to 150 degrees C. It is found that the variations of the crystalline fraction f(c), bonded Hydrogen content C(H), optical bandgap E(Tauc), film microstructure and growth rate R(d) are closely related to the substrate temperature. In particular, at a substrate temperature of 300 degrees C, the nanocrystalline Si thin films of our interest feature a high growth rate of 1.63 nm s(-1), a low Hydrogen content of 4.0 at.%, a high crystalline fraction of 69.1%, a low optical bandgap of 1.55 eV and an almost vertically aligned columnar structure with a mean grain size of approximately 10 nm. It is also shown that the low-temperature synthesis of nanocrystalline Si thin films without any Hydrogen Dilution is attributed to the outstanding dissociation ability of the high-density inductively coupled plasmas and effective plasma-surface interactions during the growth process. Our results offer a highly effective yet simple and environmentally friendly technique to synthesize high-quality nanocrystalline Si films, vitally needed for the development of new-generation solar cells and other emerging nanotechnologies.
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rapid low temperature synthesis of nc si in high density non equilibrium plasmas enabling nanocrystallinity at very low Hydrogen Dilution
Science & Engineering Faculty, 2009Co-Authors: Qijin Cheng, Shuyan Xu, Kostya OstrikovAbstract:Nanocrystalline silicon thin films were deposited on single-crystal silicon and glass substrates simultaneously by inductively coupled plasma-assisted chemical vapor deposition from the reactive silane reactant gas diluted with Hydrogen at a substrate temperature of 200 °C. The effect of Hydrogen Dilution ratio X (X is defined as the flow rate ratio of Hydrogen to silane gas), ranging from 1 to 20, on the structural and optical properties of the deposited films, is extensively investigated by Raman spectroscopy, X-ray diffraction, Fourier transform infrared absorption spectroscopy, UV/VIS spectroscopy, and scanning electron microscopy. Our experimental results reveal that, with the increase of the Hydrogen Dilution ratio X, the deposition rate Rd and Hydrogen content CH are reduced while the crystalline fraction Fc, mean grain size δ and optical bandgap ETauc are increased. In comparison with other plasma enhanced chemical vapor deposition methods of nanocrystalline silicon films where a very high Hydrogen Dilution ratio X is routinely required (e.g. X > 16), we have achieved nanocrystalline silicon films at a very low Hydrogen Dilution ratio of 1, featuring a high deposition rate of 1.57 nm/s, a high crystalline fraction of 67.1%, a very low Hydrogen content of 4.4 at.%, an optical bandgap of 1.89 eV, and an almost vertically aligned columnar structure with a mean grain size of approximately 19 nm. We have also shown that a sufficient amount of atomic Hydrogen on the growth surface essential for the formation of nanocrystalline silicon is obtained through highly-effective dissociation of silane and Hydrogen molecules in the high-density inductively coupled plasmas. © 2009 The Royal Society of Chemistry.
Subhendu Guha - One of the best experts on this subject based on the ideXlab platform.
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amorphous and nanocrystalline silicon thin film photovoltaic technology on flexible substrates
Journal of Vacuum Science and Technology, 2012Co-Authors: Baojie Yan, Jeffrey Yang, Subhendu GuhaAbstract:This paper reviews our thin film silicon-based photovoltaic (PV) technology, including material and device studies as well as roll-to-roll manufacturing on a flexible substrate. Our current thin film silicon PV products are made with Hydrogenated amorphous silicon (a-Si:H) and amorphous silicon germanium (a-SiGe:H) alloys. The advantages of a-Si:H-based technology are low cost, capability of large scale manufacturing, abundance of raw materials, and no environmental concerns. One disadvantage of a-Si:H PV technology is lower energy conversion efficiency than solar panels made of crystalline and polycrystalline silicon and compound crystal thin film semiconductors. Significant efforts have been made to improve efficiency. First, a-Si:H and a-SiGe:H material quality has been improved by optimizing deposition conditions, especially using high Hydrogen Dilution to deposit the amorphous materials close to the amorphous/nanocrystalline transition. Second, cell efficiency has been improved by engineering the dev...
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correlation of Hydrogen Dilution profiling to material structure and device performance of Hydrogenated nanocrystalline silicon solar cells
MRS Proceedings, 2008Co-Authors: Baojie Yan, Guozhen Yue, Yanfa Yan, Chunsheng Jiang, Charles W Teplin, Jeffrey Yang, Subhendu GuhaAbstract:We present a systematic study on the correlation of Hydrogen Dilution profiles to structural properties materials and solar cell performance in nc-Si:H solar cells. We deposited nc-Si:H single-junction solar cells using a modified very high frequency (VHF) glow discharge technique on stainless steel substrates with various profiles of Hydrogen Dilution in the gas mixture during deposition. The material properties were characterized using Raman spectroscopy, X-TEM, AFM, and C-AFM. The solar cell performance correlates well with the material structures. Three major conclusions are made based on the characterization results. First, the optimized nc-Si:H material does not show an incubation layer, indicating that the seeding layer is well optimized and works as per design. Second, the nanocrystalline evolution is well controlled by Hydrogen Dilution profiling in which the Hydrogen Dilution ratio is dynamically reduced during the intrinsic layer deposition. Third, the best nc-Si:H single-junction solar cell was made using a proper Hydrogen Dilution profile, which caused a nanocrystalline distribution close to uniform throughout the thickness, but with a slightly inverse nanocrystalline evolution. We have used the optimized Hydrogen Dilution profiling and improved the nc-Si:H solar cell performance significantly. As a result, we have achieved an initial active-area cell efficiency of 9.2% with a nc-Si:H single-junction structure, and 15.4% with an a-Si:H/a-SiGe:H/nc-Si:H triple-junction solar cell structure.
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material structure and metastability of Hydrogenated nanocrystalline silicon solar cells
Applied Physics Letters, 2006Co-Authors: Guozhen Yue, Subhendu Guha, Gautam Ganguly, Baojie Yan, Jeffrey Yang, Charles W TeplinAbstract:We find that the volume fraction of amorphous component in Hydrogenated nanocrystalline silicon intrinsic layers is not necessarily the determining factor for the light-induced metastability ofn-i-p solar cells. Small grains and/or intermediate range order may play an important role in improving the stability. The distribution of nanocrystallites along the growth direction is also important. Based on the findings, we have optimized the Hydrogen Dilution profiling for controlling the structural evolution and have reduced the light-induced degradation of solar cells. As a result, we have achieved initial and stable active-area efficiencies of 14.1% and 13.2%, respectively, using ana-Si:H/nc-Si:H/nc-Si:H triple-junction structure.
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Hydrogen Dilution profiling for Hydrogenated microcrystalline silicon solar cells
Applied Physics Letters, 2004Co-Authors: J. Yang, D. L. Williamson, Subhendu Guha, C S JiangAbstract:The structural properties of Hydrogenated microcrystalline silicon solar cells are investigated using Raman, x-ray diffraction, and atomic force microscopy. The experimental results showed a significant increase of microcrystalline volume fraction and grain size with increasing film thickness. The correlation between the cell performance and the microstructure suggests that the increase of grain size and microcrystalline volume fraction with thickness is the main reason for the deterioration of cell performance as the intrinsic layer thickness increases. By varying the Hydrogen Dilution in the gas mixture during deposition, microstructure evolution has been controlled and cell performance significantly improved.
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effect of Hydrogen Dilution on the structure of amorphous silicon alloys
Applied Physics Letters, 1997Co-Authors: D V Tsu, Stanford R Ovshinsky, Subhendu Guha, B S Chao, J. YangAbstract:We investigate why high levels of Hydrogen Dilution of the process gas lead to enhanced light soaking stability of amorphous silicon (a-Si) alloy solar cells by studying the microstructural properties of the material using high-resolution transmission electron microscopy (TEM) and Raman spectroscopy. The TEM results show that a-Si alloy (with or without Hydrogen Dilution) is a heterogeneous mixture of amorphous network and linear-like objects that show evidence of order along their length. The volume fraction of these ordered regions increases with increasing Hydrogen Dilution.
J. Yang - One of the best experts on this subject based on the ideXlab platform.
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Hydrogen Dilution profiling for Hydrogenated microcrystalline silicon solar cells
Applied Physics Letters, 2004Co-Authors: J. Yang, D. L. Williamson, Subhendu Guha, C S JiangAbstract:The structural properties of Hydrogenated microcrystalline silicon solar cells are investigated using Raman, x-ray diffraction, and atomic force microscopy. The experimental results showed a significant increase of microcrystalline volume fraction and grain size with increasing film thickness. The correlation between the cell performance and the microstructure suggests that the increase of grain size and microcrystalline volume fraction with thickness is the main reason for the deterioration of cell performance as the intrinsic layer thickness increases. By varying the Hydrogen Dilution in the gas mixture during deposition, microstructure evolution has been controlled and cell performance significantly improved.
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amorphous silicon alloy materials and solar cells near the threshold of microcrystallinity
MRS Proceedings, 1999Co-Authors: J. Yang, S. GuhaAbstract:One of the most effective techniques used to obtain high quality amorphous silicon alloys is the use of Hydrogen Dilution during film growth. The resultant material exhibits a more ordered microstructure and gives rise to high efficiency solar cells. As the Hydrogen Dilution increases, however, a threshold is reached, beyond which microcrystallites begin to form rapidly. In this paper, they review some of the interesting features associated with the thin film materials obtained from various Hydrogen Dilutions. They include the observation of linear-like objects in the TEM micrograph, a shift of the principal Si TO band in the Raman spectrum, a sharp, low temperature peak in the H{sub 2} evolution spectrum, a shift of the wagging mode in the IR spectrum, and a narrowing of the Si(111) peak in the X-ray diffraction pattern. These spectroscopic tools have allowed them to optimize deposition conditions to near the threshold of microcrystallinity and obtain desired high quality materials. Incorporation of the improved materials into device configuration has significantly enhanced the solar cell performance. Using a spectral-splitting, triple-junction configuration, the spectral response of a typical high efficiency device spans from below 350 nm to beyond 950 nm with a peak quantum efficiency exceeding 90%;more » the triple stack generates a photocurrent of 27 mA/cm{sup 2}. This paper describes the effect of the improved materials on various solar cell structures, including a 13% active-area, stable triple-junction device.« less
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effect of Hydrogen Dilution on the structure of amorphous silicon alloys
Applied Physics Letters, 1997Co-Authors: D V Tsu, Stanford R Ovshinsky, Subhendu Guha, B S Chao, J. YangAbstract:We investigate why high levels of Hydrogen Dilution of the process gas lead to enhanced light soaking stability of amorphous silicon (a-Si) alloy solar cells by studying the microstructural properties of the material using high-resolution transmission electron microscopy (TEM) and Raman spectroscopy. The TEM results show that a-Si alloy (with or without Hydrogen Dilution) is a heterogeneous mixture of amorphous network and linear-like objects that show evidence of order along their length. The volume fraction of these ordered regions increases with increasing Hydrogen Dilution.
