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Nanopyramid Formation by Ag Metal-Assisted Chemical Etching for Nanotextured Si Solar Cells
Bhaskar Parida,김근주,최재호,Srikanta Palei,곽승종 한국전기전자재료학회 2015 Transactions on Electrical and Electronic Material Vol.16 No.4
We investigated the formation of a nanopyramidal structure and fabricated nanotextured Si solar cells using an Ag metal-assisted chemical etching process. The nanopyramidal structure was formed on a Si flat surface and the nanotexturing process was performed on the p-type microtextured Si surface. The nanostructural formation shows a transition from nanopits and nanopores to nanowires with etching time. The nanotextured surfaces also showed the photoluminescence spectra with an enhanced intensity in the wavelength range of 1,100~1,250 nm. The photoreflectance of the nanotextured Si solar cells was strongly reduced in the wavelength range of 337~596 nm. However, the quantum efficiency is decreased in the nanotextured samples due to the increased nanosurface recombination. The nanotexturing process provides a better p-n junction impedance of the nanotextured cells, resulting in an enhanced shunt resistance and fill factor which in turn renders the possibility of the increased conversion efficiency.
Bhaskar Parida,김근주,최재호,Srikanta Palei,곽승종 한국전기전자재료학회 2015 Transactions on Electrical and Electronic Material Vol.16 No.4
We investigated nanotextured Si solar cells using the silver-assisted chemical etching process. The nanotexturing process is very sensitive to the concentration of chemical etching solution. The high concentration process results in a nanowire formation for the nanosurfaces and causes severe surface damage to the top region of the micropyramids. These nanowires show excellent light absorption in photoreflectance spectra and radiative light emission in photoluminescence spectra. However, the low concentration process forms a nano-roughened surface and provides high minority carrier lifetimes. The nano-roughened surfaces of the samples show the improved electrical cell properties of quantum efficiency, conversion efficiency, and cell fill factor due to the reduction in the formation of the over-doped dead layer.
Nanocatalytic growth of Si nanowires from Ni silicate coated SiC nanoparticles on Si solar cell.
Parida, Bhaskar,Choi, Jaeho,Ji, Hyung Yong,Park, Seungil,Lim, Gyoungho,Kim, Keunjoo American Scientific Publishers 2013 Journal of Nanoscience and Nanotechnology Vol.13 No.9
<P>We investigated the nanocatalytic growth of Si nanowires on the microtextured surface of crystalline Si solar cell. 3C-SiC nanoparticles have been used as the base for formation of Ni silicate layer in a catalytic reaction with the Si melt under H2 atmosphere at an annealing temperature of 1100 degrees C. The 10-nm thick Ni film was deposited after the SiC nanoparticles were coated on the microtextured surface of the Si solar cell by electron-beam evaporation. SiC nanoparticles form a eutectic alloy surface of Ni silicate and provide the base for Si supersaturation as well as the Ni-Si alloy layer on Si substrate surface. This bottom reaction mode for the solid-liquid-solid growth mechanism using a SiC nanoparticle base provides more stable growth of nanowires than the top reaction mode growth mechanism in the absence of SiC nanoparticles. Thermally excited Ni nanoparticle forms the eutectic alloy and provides collectively excited electrons at the alloy surface, which reduces the activation energy of the nanocatalytic reaction for formation of nanowires.</P>
Parida, Bhaskar,Choi, Jaeho,Lim, Gyoungho,Park, Seungil,Kim, Keunjoo American Scientific Publishers 2014 Journal of Nanoscience and Nanotechnology Vol.14 No.12
<P>We investigated a nanotexturization process on the microtextured surface of monocrystalline Si solar cells which utilized a metal assisted chemical etching process. P-type Si solar cell wafers were used for nanotexturing followed by saw damage removal and a microtexturing process. As the nanotexturing time was increased, green and red-orange photoluminescence spectra at wavelengths of 506, 507, and 637 nm were observed from the nanotextured cells, indicating that the quantum size effect caused the confinement of charge carriers in nanocrystalline silicon. The nanotextured cells showed a low photoreflectance of 4.5% in the visible spectral region of 400-600 nm. However, the reduced quantum efficiency from the nanotextured samples suggests that a shallow nanopore depth and density are required to prevent surface-related phenomena of charge recombination and surface current leakage.</P>
Bhaskar Parida,Seonghoon Jeong,Hyunsoo Kim 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.73 No.7
The effects of post-thermal diffusion of Al into heavily Al-doped ZnO (AZO) on its electrical, optical, and structural properties were investigated. Notably, the thermal diffusion of Al led to a significant enhancement of the optical transmittance-e.g., the transmittances at 550 nm were 90.4% and 96.7% before and after Al thermal diffusion, respectively. The structural analysis revealed that the improved optical transmittance was due to the combined effects of improved crystallinity, smoother surface, and the presence of transparent Al-O. However, the electrical properties of the AZO films after Al thermal diffusion were degraded-e.g., the sheet resistance was increased by 24% after thermal diffusion, which might be attributed to the generation of internal defects due to the heavy Al doping.
Parida, Bhaskar,Choi, Jaeho,Palei, Srikanta,Kim, Keunjoo,Kwak, Seung Jong The Korean Institute of Electrical and Electronic 2015 Transactions on Electrical and Electronic Material Vol.16 No.4
We investigated nanotextured Si solar cells using the silver-assisted chemical etching process. The nanotexturing process is very sensitive to the concentration of chemical etching solution. The high concentration process results in a nanowire formation for the nanosurfaces and causes severe surface damage to the top region of the micropyramids. These nanowires show excellent light absorption in photoreflectance spectra and radiative light emission in photoluminescence spectra. However, the low concentration process forms a nano-roughened surface and provides high minority carrier lifetimes. The nano-roughened surfaces of the samples show the improved electrical cell properties of quantum efficiency, conversion efficiency, and cell fill factor due to the reduction in the formation of the over-doped dead layer.
Formation of Nanopyramidal Structures on Microtextured Si Surfaces for Solar Cell Application
Parida, Bhaskar,Palei, Srikanta,Choi, Jaeho,Kim, Keunjoo American Scientific Publishers 2016 Journal of Nanoscience and Nanotechnology Vol.16 No.10
<P>We investigated the fabrication of nanopyramidal structures on microtextured Si solar cells by metal-assisted chemical and alkaline etching methods. Uniform nanoporous structures were formed on the surface of the microtextured Si solar cell sample. The depth of the nanopores was increased from 100 to 450 nm with increasing the etching time from 30 to 120 sec. The deep nanopores after alkaline etching were converted to dense nanopyramidal structures surrounding the micropyramids of the Si solar cell sample. The sizes of the nanopyramids depend on the depth of the nanopores. The dense nanopyramidal structures with SiNx coating has lower photoreflectance of 1.3% in the wavelength of 400 similar to 800 nm than the reference and the nanotextured samples. The high minority carrier lifetime of the sample with nanopyramid structures indicates that the Auger recombination and the surface recombination are minimized due to the low surface area and large opening of the nanopyramids.</P>
Parida, Bhaskar,Ryu, Jun,Yoon, Saemon,Lee, Seojun,Seo, Yejin,Cho, Jung Sang,Kang, Dong-Won The Royal Society of Chemistry 2019 Journal of Materials Chemistry A Vol.7 No.31
<P>Recently, CsPbI3−xBrx (<I>x</I> = 1-2) all-inorganic perovskites have been studied to overcome the phase instability of CsPbI3. However, the addition of Br inevitably leads to a bandgap that is too wide (1.93-2.03 eV) compared to that of CsPbI3 (1.73 eV). To avoid this, the present study focuses on developing stable α-CsPbI3−xBrx (<I>x</I> < 0.7) perovskite films with lower Br levels. Our dynamic CsBr treatment incorporates Br<SUP>−</SUP> into the CsPbI3 lattice, greatly enhancing the morphology, optical properties, stability, and photovoltaic performance of the resultant CsPbI3−xBrx (<I>x</I> < 0.7) perovskite films. At <I>x</I> = 0.66, the perovskite film with the relatively low bandgap of 1.84 eV contributes to achieving an impressive power conversion efficiency (PCE) of 14.08% and, after 1200 h storage under a nitrogen atmosphere without encapsulation, the PCE remains at around 70% of this initial level. This two-step growth using dynamic CsBr treatment opens up promising routes for the feasible fabrication of inorganic perovskite photovoltaics with exceptional stability.</P>
Nanopyramid Formation by Ag Metal-Assisted Chemical Etching for Nanotextured Si Solar Cells
Parida, Bhaskar,Choi, Jaeho,Palei, Srikanta,Kim, Keunjoo,Kwak, Seung Jong The Korean Institute of Electrical and Electronic 2015 Transactions on Electrical and Electronic Material Vol.16 No.4
We investigated the formation of a nanopyramidal structure and fabricated nanotextured Si solar cells using an Ag metal-assisted chemical etching process. The nanopyramidal structure was formed on a Si flat surface and the nanotexturing process was performed on the p-type microtextured Si surface. The nanostructural formation shows a transition from nanopits and nanopores to nanowires with etching time. The nanotextured surfaces also showed the photoluminescence spectra with an enhanced intensity in the wavelength range of 1,100~1,250 nm. The photoreflectance of the nanotextured Si solar cells was strongly reduced in the wavelength range of 337~596 nm. However, the quantum efficiency is decreased in the nanotextured samples due to the increased nanosurface recombination. The nanotexturing process provides a better p-n junction impedance of the nanotextured cells, resulting in an enhanced shunt resistance and fill factor which in turn renders the possibility of the increased conversion efficiency.