Juris P. Kalejs

Hydrogenation of Si from SiNx(H) films: Characterization of H introduced into the Si

A promising method to introduce H into multicrystalline Si solar cells in order to passivate bulk defects is by the postdeposition annealing of a H-rich, SiNx surface layer. It has previously been difficult to characterize the small concentration of H that is introduced by this method. Infrared spectroscopy has been used together with marker impurities in the Si to determine the concentration and depth of H introduced into Si from an annealed SiNx film.

Enhanced silicon solar cell performance by rapid thermal firing of screen-printed metals

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/sup +/-p-p/sup +/ 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 (S/sub eff/) of >5000 cm/s and /spl sim/1500 cm/s for co-firing in the BLP and the RTP, respectively. Two-step firing produced S/sub eff/ of /spl sim/1500 cm/s and /spl sim/700 cm/s in the BLP and the RTP, respectively. However, S/sub eff/ for the two-step firing, involving BLP BSF formation followed by RTP contact firing, was found to be /spl sim/700 cm/s, which indicates that RTP contact firing with a faster ramp-up (100/spl deg/C/s) restores the poor-quality BLP BSF. On the other hand, BLP contact firing with a slow ramp-up (<10/spl deg/C/s) degrades the high-quality RTP BSF, increasing S/sub eff/ from /spl sim/700 cm/s to /spl sim/1500 cm/s.

Hydrogenation of defects in edge-defined film-fed grown aluminum-enhanced plasma enhanced chemical vapor deposited silicon nitride multicrystalline silicon

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 850u200a°C, without the coformation of aluminum back surface field on the back, does not provide appreciable passivation or hydrogenation of bulk def...

Concentration and penetration depth of H introduced into crystalline Si by hydrogenation methods used to fabricate solar cells

The hydrogenation of crystalline Si by methods used to passivate defects in Si solar cells has been studied by infrared spectroscopy. For these experiments, floating-zone Si that contained Pt impurities that act as traps for H was used as a model system in which H could be directly detected. In this model system, the concentration and indiffusion depth of H were determined for different hydrogenation treatments so that their effectiveness could be compared. The postdeposition annealing of a hydrogen-rich SiNx surface layer was found to introduce H into the Si bulk with a concentration of ∼1015cm−3 under the best conditions investigated here.

Review on Ribbon Silicon Techniques for Cost Reduction in PV

The shortage of Si feedstock and the goal of reducing Wp costs in photovoltaics (PV) is the driving force to look for alternatives to ingot grown multicrystalline (me) Si wafers which have the highest share in the PV market. Ribbon Si seems to be a very promising candidate as no kerf losses occur, resulting in reduced Si costs per Wp. In addition, there is no need for the energy consuming crystallization of the ingot and therefore energy payback times can be significantly reduced. The higher defect density in ribbon Si materials has to be taken into account during cell processing, but ribbon materials already commercially available show excellent efficiencies, while for the most promising techniques efficiencies are significantly lower, but very promising. In this presentation an overview of ribbon Si technologies currently under research will be given, based on available data on crystal growth as well as solar cell processing and cell parameters

Infrared study of the concentration of H introduced into Si by the postdeposition annealing of a SiNx coating

The postdeposition annealing of a SiNx antireflection coating is commonly used to introduce hydrogen into a multicrystalline Si solar cell to passivate defects in the Si bulk. A quantitative comparison has been made of the concentrations of H that are introduced into a Si model system from SiNx coatings with high and low density that have been characterized by infrared spectroscopy. Experiments have also been performed in which the processing of the SiNx/Si interface was modified to compare how the preparation of the interface and properties of the SiNx film itself affect the concentration of H that is introduced into the Si bulk.

Interaction of hydrogen with carbon in multicrystalline Si solar-cell materials

Hydrogen is commonly introduced into silicon solar cells to reduce the deleterious effects of defects and to increase cell efficiency. When hydrogen is introduced into multicrystalline Si that is often used for the fabrication of solar cells, the H atoms can become trapped by carbon impurities to produce defect structures known at H2*(C). These defects act as both a source and a sink for hydrogen in H-related defect reactions. IR spectroscopy has been used to determine what H- and C-related defects are formed in multicrystalline Si when the carbon concentration is varied. A process that is used by industry to introduce hydrogen into Si solar cells is the postdeposition annealing of a hydrogen-rich SiNx layer. The H2*(C) defects provide a strategy for estimating the concentration and penetration depth of the hydrogen that is introduced by this method.

Hydrogen Passivation of Defects in Crystalline Silicon Solar Cells

Hydrogen is commonly introduced into silicon solar cells to reduce the deleterious effects of defects and to increase cell efficiency. We have developed strategies by which hydrogen in silicon can be detected by IR spectroscopy with high sensitivity. The introduction of hydrogen into Si by the post-deposition annealing of a hydrogen-rich, SiN x coating has been investigated to determine hydrogens concentration and penetration depth. Different hydrogenation processes were studied so that their effectiveness for the passivation of bulk defects could be compared. The best conditions investigated in our experiments yielded a hydrogen concentration near 10 15 cm -3 and a diffusion depth consistent with the diffusivity of H found by Van Wieringen and Warmoltz.

A National Photovoltaic Industry Assessment for the Usa: Needs, Corporate Structure and Building Blocks

The semiconductor industry is often used as a template for gauging progress and to provide a guide for development of both manufacturing and business models for crystalline silicon-based photovoltaic (PV) technology, which currently comprise over 85% of the PV industry. We offer insight into how the US can leverage existing semiconductor industry organizational knowledge and manufacturing infrastructure and propose a process for bootstrapping applicable elements which could help this dominant segment of the US PV Industry to recover its leadership position in the global marketplace

Reactions of H with C in Multicrystalline Si Solar-cell Materials

Hydrogen is commonly introduced into silicon solar cells to reduce the deleterious effects of defects and to increase cell efficiency. When hydrogen is introduced into multicrystalline Si that is often used for the fabrication of solar cells, the H atoms become trapped by carbon impurities to produce defect structures known at H 2 *(C). These defects act as both a source and a sink for hydrogen in H-related defect reactions. IR spectroscopy has been used to determine what H- and C-related defects are formed in multicrystalline Si when the carbon concentration is varied. A process that is used by industry to introduce hydrogen into Si solar cells is the post-deposition annealing of a hydrogen-rich SiNx layer. The H 2 *(C) defects provide a strategy for estimating the concentration and penetration depth of the hydrogen that is introduced by this method.