Mark Rosenblum - Academia.edu (original) (raw)
Papers by Mark Rosenblum
Solar Energy Materials and Solar Cells, 2002
A low-cost, manufacturable defect gettering and passivation treatment, involving simultaneous ann... more A low-cost, manufacturable defect gettering and passivation treatment, involving simultaneous anneal of a PECVD SiN x film and a screen-printed Al layer, is found to improve the lifetime in Si ribbon materials from 1-10 µs to over 20 µs. Our results indicate that the optimum anneal temperature for SiN x-induced hydrogenation is 700°C for EFG and increases to 825°C when Al is present on the back of the sample. This not only improves the degree of hydrogenation, but also forms an effective back surface field. We propose a three-step physical model, based our results, in which defect passivation is governed by the release of hydrogen from the SiN x film due to annealing, the generation of vacancies during Al-Si alloying, and the retention of hydrogen at defect sites due to rapid cooling. Controlled rapid cooling was implemented after the hydrogenation anneal to improve the retention of hydrogen at defect sites by incorporating an RTP contact firing scheme. RTP contact firing improved the performance of ribbon solar cells by 1.3-1.5% absolute when compared to slow, belt furnace contact firing. This enhancement was due to improved back surface recombination velocity, fill factor, and bulk lifetime. Enhanced hydrogenation and rapid heating and cooling resulted in screen-printed Si ribbon cell efficiencies approaching 15%.
MRS Proceedings, 1996
Interactions between structural defects and metallic impurities were studied in multicrystalline ... more Interactions between structural defects and metallic impurities were studied in multicrystalline silicon for solar cell applications. The objective was to gain insight into the relationship between solar cell processing, metallic impurity behavior and the resultant effect on material/device performance. With an intense synchrotron x-ray source, high sensitivity x-ray fluorescence measurements were utilized to determine impurity distributions with a spatial resolution of ≈ lμm. Diffusion length mapping and final solar cell characteristics gauged material/device performance. The materials were tested in both the as-grown state and after full solar cell processing. Iron and nickel metal impurities were located at structural defects in asgrown material, while after solar cell processing, both impurities were still observed in low performance regions. These results indicate that multicrystalline silicon solar cell performance is directly related to metal impurities which are not complete...
Conference Record of the Twenty-Eighth IEEE Photovoltaic Specialists Conference - 2000 (Cat. No.00CH37036), 2000
P and Al gettering and SiN-induced hydrogenation of EFG Si have been investigated using manufactu... more P and Al gettering and SiN-induced hydrogenation of EFG Si have been investigated using manufacturable process techniques. Annealing of SiN coated EFG, without Al on the back, shows very little defect passivation with maximum lifetime enhancement at 700/spl deg/C. However, annealing of the SiN film, in the presence of Al, significantly increases the defect passivation and moves the optimum temperature to above 800/spl deg/C. This increase in the optimum temperature is the result of tradeoff between the increase in the release of hydrogen from the SiN film and the decrease in the retention of hydrogen at defects at high temperatures. A higher annealing temperature (>800/spl deg/C) is desirable because it produces a superior Al-BSF without sacrificing defect passivation. Finally, it is shown that the efficacy of the gettering and hydrogenation process is a strong function of the as-grown lifetime, which dictates the final lifetime as well as cell efficiency.
New Journal of Chemistry, 1987
Les problemes rencontres en photoelectrochimie des semiconducteurs sont rapportes: developpement ... more Les problemes rencontres en photoelectrochimie des semiconducteurs sont rapportes: developpement de cellules solaires a jonction n-Si/liquide; croissance photoelectrochimique des cellules de type MIS; etude de la chimie interfaciale des materiaux III-V; processus chimiques pour minimiser les pertes de recombinaison aux joints de grain et aux etats de surface des interfaces de Si et de GaAs
Conference Record of the Twenty-Ninth IEEE Photovoltaic Specialists Conference, 2002.
We report here on advances made in EFG technology over a 3-year PVMaT 5A2 NREL subcontract. We de... more We report here on advances made in EFG technology over a 3-year PVMaT 5A2 NREL subcontract. We describe improvements to lower module costs through raising cell efficiencies to 14% and reduction of mechanical and electrical losses. Plasma etching of the laser-cut wafer edges has reduced acid use by >50%. We have introduced 10 cm × 15 cm wafers into manufacturing,
Conference Record of the Twenty Fifth IEEE Photovoltaic Specialists Conference - 1996, 1996
We conducted an investigation of plasma deposition and etching processes on full-size multicrysta... more We conducted an investigation of plasma deposition and etching processes on full-size multicrystalline (mc-Si) cells processed in commercial production lines, so that any improvements obtained will be immediately relevant to the PV industry. In one case, we performed a statistically designed multiparameter experiment to determine the optimum PECVDnitride deposition conditions specific to EFG silicon from ASE Americas, Inc. In a related effort, we studied whether plasma-etching techniques can use standard screen-printed gridlines as etch masks to form self-aligned, pattemed-emitter profiles on moSi cells from Solarex Corp. Our initial results found a statistically significant improvement of about half an absolute percentage point in cell efficiency when the self-aligned emitter etchback was combined with the PECVD-nitride surface passivation treatment, Additional improvement is expected when the successful bulk passivation treatment is also added to the process.
Journal of Applied Physics, 2000
Gettering of impurities and hydrogen passivation of defects in edge-defined film-fed grown (EFG) ... more Gettering of impurities and hydrogen passivation of defects in edge-defined film-fed grown (EFG) multicrystalline silicon were studied by low-cost manufacturable technologies such as emitter diffusion by a spin-on phosphorus dopant source, back surface field formation by screen-printed aluminum, and a post-deposition anneal of plasma enhanced chemical vapor deposited (PECVD) silicon nitride antireflection coating. These processes were carried out in a high-throughput lamp-heated conveyor belt furnace. PECVD silicon nitride-induced hydrogenation of defects in EFG silicon was studied in conjunction with screen-printed aluminum back surface field formation to investigate the synergistic effect of aluminum gettering and silicon nitride hydrogenation of bulk defects. It was found that post-deposition anneal of PECVD silicon nitride at temperatures ranging from 450 to 850 °C, without the coformation of aluminum back surface field on the back, does not provide appreciable passivation or hy...
IEEE Transactions on Electron Devices, 2001
Rapid thermal processing (RTP) of screen-printed (SP) Al on the back and silver (Ag) grid on the ... more Rapid thermal processing (RTP) of screen-printed (SP) Al on the back and silver (Ag) grid on the front produced significant improvement in back surface field (BSF) of n +-p-p + float-zone (FZ) Si solar cells. Two-step firing was found to form more effective BSF than co-firing, resulting in 0.6-1.0% increase in absolute cell efficiency. In addition, RTP was found to be more effective than the beltline processing (BLP), resulting in 0.5-1.0% increase in absolute cell efficiency. Although the Al-BSF formed by the BLP was inferior to the RTP, the difference between the two is virtually eliminated during the subsequent RTP contact firing. Internal quantum efficiency (IQE) analysis of the solar cells gave effective back surface recombination velocities (e) of 5000 cm/s and 1500 cm/s for co-firing in the BLP and the RTP, respectively. Two-step firing produced e of 1500 cm/s and 700 cm/s in the BLP and the RTP, respectively. However, e for the two-step firing, involving BLP BSF formation followed by RTP contact firing, was found to be 700 cm/s, which indicates that RTP contact firing with a faster ramp-up (100 C/s) restores the poor-quality BLP BSF. On the other hand, BLP contact firing with a slow ramp-up (10 C/s) degrades the high-quality RTP BSF, increasing e from 700 cm/s to 1500 cm/s.
Applied Physics Letters, 1990
A photoelectrochemical anodization technique has been used to fabricate n-Si/insulator/metal (MIS... more A photoelectrochemical anodization technique has been used to fabricate n-Si/insulator/metal (MIS) diodes with improved electrical properties. MIS structures fabricated with Au have provided the first experimental observation of a solid-state n-Si surface barrier device whose open circuit voltage Voc is controlled by minority-carrier bulk diffusion/recombination processes. For these diodes, variation of the minority-carrier diffusion length and majority-carrier dopant density produced changes in Voc that were in accord with bulk diffusion/recombination theory. Additionally, the variation in Voc in response to changes in the work function of the metal overlayer indicated that these MIS devices were not subject to the Fermi level pinning restrictions observed for n-Si Schottky structures. X-ray photoelectron spectroscopic characterization of the anodically grown insulator indicated 8.2±0.9 Å of a strained SiO2 layer as the interfacial insulator resulting from the photoanodization proc...
The Journal of Physical Chemistry, 1984
3103 troduced as contamination either during the deposition or in subsequent handling. This carbo... more 3103 troduced as contamination either during the deposition or in subsequent handling. This carbon contamination must be taken into account in evaluating the results of these analyses. Phenylsilane, on the other hand, produced a thick deposit having a nodular appearance (shown in Figure 6a). After a few atomic layers of oxidized material are stripped away by Ar+ sputtering, an average film composition of-75 atom % C,-18 atom %Si, and-7 atom % 0 was encountered, which extended uniformly to a depth of many hundreds, perhaps even thousands, of angstroms. Ag was barely seen, even after extensive Ar+ sputtering, indicating nearly complete surface coverage. The deposit from MIRPD of phenylsilane was not entirely uniform, however. X-ray fluorescence analysis of the material shown in Figure 6a establishes that the lumps of nodules which were observed are silicon-rich material, while the "valleys" between the nodules are poorer in Si and richer in C. A similar nodular appearance, but on a much larger scale, has been observed in products of C W laser heating of SiCl:' or of silane/ammonia mixtures.32 Breiland et al. have observed33 formation of gaseous Siz during silane CVD; these dimers could presumably go on to form silicon clusters prior to deposition. An extreme case of nonuniform deposition is illustrated in Figure 6b, which is an SEM of material deposited on Ag by MIRPD of disilane. In this case, the material has deposited as discrete nodules directly on the Ag surface: presumably, the square symmetric structures result from preferential nucleation a t grain boundaries of Ag crystallites. Conclusions and Discussion In this work, we have shown that the laser-induced unimolecular decomposition of alkylsilanes proceeds via a four-center elimination (31) V. Baranauskas, C.
Solar Energy Materials and Solar Cells, 2002
A low-cost, manufacturable defect gettering and passivation treatment, involving simultaneous ann... more A low-cost, manufacturable defect gettering and passivation treatment, involving simultaneous anneal of a PECVD SiN x film and a screen-printed Al layer, is found to improve the lifetime in Si ribbon materials from 1-10 µs to over 20 µs. Our results indicate that the optimum anneal temperature for SiN x-induced hydrogenation is 700°C for EFG and increases to 825°C when Al is present on the back of the sample. This not only improves the degree of hydrogenation, but also forms an effective back surface field. We propose a three-step physical model, based our results, in which defect passivation is governed by the release of hydrogen from the SiN x film due to annealing, the generation of vacancies during Al-Si alloying, and the retention of hydrogen at defect sites due to rapid cooling. Controlled rapid cooling was implemented after the hydrogenation anneal to improve the retention of hydrogen at defect sites by incorporating an RTP contact firing scheme. RTP contact firing improved the performance of ribbon solar cells by 1.3-1.5% absolute when compared to slow, belt furnace contact firing. This enhancement was due to improved back surface recombination velocity, fill factor, and bulk lifetime. Enhanced hydrogenation and rapid heating and cooling resulted in screen-printed Si ribbon cell efficiencies approaching 15%.
MRS Proceedings, 1996
Interactions between structural defects and metallic impurities were studied in multicrystalline ... more Interactions between structural defects and metallic impurities were studied in multicrystalline silicon for solar cell applications. The objective was to gain insight into the relationship between solar cell processing, metallic impurity behavior and the resultant effect on material/device performance. With an intense synchrotron x-ray source, high sensitivity x-ray fluorescence measurements were utilized to determine impurity distributions with a spatial resolution of ≈ lμm. Diffusion length mapping and final solar cell characteristics gauged material/device performance. The materials were tested in both the as-grown state and after full solar cell processing. Iron and nickel metal impurities were located at structural defects in asgrown material, while after solar cell processing, both impurities were still observed in low performance regions. These results indicate that multicrystalline silicon solar cell performance is directly related to metal impurities which are not complete...
Conference Record of the Twenty-Eighth IEEE Photovoltaic Specialists Conference - 2000 (Cat. No.00CH37036), 2000
P and Al gettering and SiN-induced hydrogenation of EFG Si have been investigated using manufactu... more P and Al gettering and SiN-induced hydrogenation of EFG Si have been investigated using manufacturable process techniques. Annealing of SiN coated EFG, without Al on the back, shows very little defect passivation with maximum lifetime enhancement at 700/spl deg/C. However, annealing of the SiN film, in the presence of Al, significantly increases the defect passivation and moves the optimum temperature to above 800/spl deg/C. This increase in the optimum temperature is the result of tradeoff between the increase in the release of hydrogen from the SiN film and the decrease in the retention of hydrogen at defects at high temperatures. A higher annealing temperature (>800/spl deg/C) is desirable because it produces a superior Al-BSF without sacrificing defect passivation. Finally, it is shown that the efficacy of the gettering and hydrogenation process is a strong function of the as-grown lifetime, which dictates the final lifetime as well as cell efficiency.
New Journal of Chemistry, 1987
Les problemes rencontres en photoelectrochimie des semiconducteurs sont rapportes: developpement ... more Les problemes rencontres en photoelectrochimie des semiconducteurs sont rapportes: developpement de cellules solaires a jonction n-Si/liquide; croissance photoelectrochimique des cellules de type MIS; etude de la chimie interfaciale des materiaux III-V; processus chimiques pour minimiser les pertes de recombinaison aux joints de grain et aux etats de surface des interfaces de Si et de GaAs
Conference Record of the Twenty-Ninth IEEE Photovoltaic Specialists Conference, 2002.
We report here on advances made in EFG technology over a 3-year PVMaT 5A2 NREL subcontract. We de... more We report here on advances made in EFG technology over a 3-year PVMaT 5A2 NREL subcontract. We describe improvements to lower module costs through raising cell efficiencies to 14% and reduction of mechanical and electrical losses. Plasma etching of the laser-cut wafer edges has reduced acid use by >50%. We have introduced 10 cm × 15 cm wafers into manufacturing,
Conference Record of the Twenty Fifth IEEE Photovoltaic Specialists Conference - 1996, 1996
We conducted an investigation of plasma deposition and etching processes on full-size multicrysta... more We conducted an investigation of plasma deposition and etching processes on full-size multicrystalline (mc-Si) cells processed in commercial production lines, so that any improvements obtained will be immediately relevant to the PV industry. In one case, we performed a statistically designed multiparameter experiment to determine the optimum PECVDnitride deposition conditions specific to EFG silicon from ASE Americas, Inc. In a related effort, we studied whether plasma-etching techniques can use standard screen-printed gridlines as etch masks to form self-aligned, pattemed-emitter profiles on moSi cells from Solarex Corp. Our initial results found a statistically significant improvement of about half an absolute percentage point in cell efficiency when the self-aligned emitter etchback was combined with the PECVD-nitride surface passivation treatment, Additional improvement is expected when the successful bulk passivation treatment is also added to the process.
Journal of Applied Physics, 2000
Gettering of impurities and hydrogen passivation of defects in edge-defined film-fed grown (EFG) ... more Gettering of impurities and hydrogen passivation of defects in edge-defined film-fed grown (EFG) multicrystalline silicon were studied by low-cost manufacturable technologies such as emitter diffusion by a spin-on phosphorus dopant source, back surface field formation by screen-printed aluminum, and a post-deposition anneal of plasma enhanced chemical vapor deposited (PECVD) silicon nitride antireflection coating. These processes were carried out in a high-throughput lamp-heated conveyor belt furnace. PECVD silicon nitride-induced hydrogenation of defects in EFG silicon was studied in conjunction with screen-printed aluminum back surface field formation to investigate the synergistic effect of aluminum gettering and silicon nitride hydrogenation of bulk defects. It was found that post-deposition anneal of PECVD silicon nitride at temperatures ranging from 450 to 850 °C, without the coformation of aluminum back surface field on the back, does not provide appreciable passivation or hy...
IEEE Transactions on Electron Devices, 2001
Rapid thermal processing (RTP) of screen-printed (SP) Al on the back and silver (Ag) grid on the ... more Rapid thermal processing (RTP) of screen-printed (SP) Al on the back and silver (Ag) grid on the front produced significant improvement in back surface field (BSF) of n +-p-p + float-zone (FZ) Si solar cells. Two-step firing was found to form more effective BSF than co-firing, resulting in 0.6-1.0% increase in absolute cell efficiency. In addition, RTP was found to be more effective than the beltline processing (BLP), resulting in 0.5-1.0% increase in absolute cell efficiency. Although the Al-BSF formed by the BLP was inferior to the RTP, the difference between the two is virtually eliminated during the subsequent RTP contact firing. Internal quantum efficiency (IQE) analysis of the solar cells gave effective back surface recombination velocities (e) of 5000 cm/s and 1500 cm/s for co-firing in the BLP and the RTP, respectively. Two-step firing produced e of 1500 cm/s and 700 cm/s in the BLP and the RTP, respectively. However, e for the two-step firing, involving BLP BSF formation followed by RTP contact firing, was found to be 700 cm/s, which indicates that RTP contact firing with a faster ramp-up (100 C/s) restores the poor-quality BLP BSF. On the other hand, BLP contact firing with a slow ramp-up (10 C/s) degrades the high-quality RTP BSF, increasing e from 700 cm/s to 1500 cm/s.
Applied Physics Letters, 1990
A photoelectrochemical anodization technique has been used to fabricate n-Si/insulator/metal (MIS... more A photoelectrochemical anodization technique has been used to fabricate n-Si/insulator/metal (MIS) diodes with improved electrical properties. MIS structures fabricated with Au have provided the first experimental observation of a solid-state n-Si surface barrier device whose open circuit voltage Voc is controlled by minority-carrier bulk diffusion/recombination processes. For these diodes, variation of the minority-carrier diffusion length and majority-carrier dopant density produced changes in Voc that were in accord with bulk diffusion/recombination theory. Additionally, the variation in Voc in response to changes in the work function of the metal overlayer indicated that these MIS devices were not subject to the Fermi level pinning restrictions observed for n-Si Schottky structures. X-ray photoelectron spectroscopic characterization of the anodically grown insulator indicated 8.2±0.9 Å of a strained SiO2 layer as the interfacial insulator resulting from the photoanodization proc...
The Journal of Physical Chemistry, 1984
3103 troduced as contamination either during the deposition or in subsequent handling. This carbo... more 3103 troduced as contamination either during the deposition or in subsequent handling. This carbon contamination must be taken into account in evaluating the results of these analyses. Phenylsilane, on the other hand, produced a thick deposit having a nodular appearance (shown in Figure 6a). After a few atomic layers of oxidized material are stripped away by Ar+ sputtering, an average film composition of-75 atom % C,-18 atom %Si, and-7 atom % 0 was encountered, which extended uniformly to a depth of many hundreds, perhaps even thousands, of angstroms. Ag was barely seen, even after extensive Ar+ sputtering, indicating nearly complete surface coverage. The deposit from MIRPD of phenylsilane was not entirely uniform, however. X-ray fluorescence analysis of the material shown in Figure 6a establishes that the lumps of nodules which were observed are silicon-rich material, while the "valleys" between the nodules are poorer in Si and richer in C. A similar nodular appearance, but on a much larger scale, has been observed in products of C W laser heating of SiCl:' or of silane/ammonia mixtures.32 Breiland et al. have observed33 formation of gaseous Siz during silane CVD; these dimers could presumably go on to form silicon clusters prior to deposition. An extreme case of nonuniform deposition is illustrated in Figure 6b, which is an SEM of material deposited on Ag by MIRPD of disilane. In this case, the material has deposited as discrete nodules directly on the Ag surface: presumably, the square symmetric structures result from preferential nucleation a t grain boundaries of Ag crystallites. Conclusions and Discussion In this work, we have shown that the laser-induced unimolecular decomposition of alkylsilanes proceeds via a four-center elimination (31) V. Baranauskas, C.