Analysis of Dislocation Networks and Electronic Properties of Dendritic Web Silicon

AbstractDuring the growth of dendritic web silicon, an ideal material for fabrication of high efficiency solar cells, a thin ribbon of silicon single crystal is obtained. Due to thermal stresses characteristic in this growth process, dislocations and residual stresses are observed in most ribbons. In this study, transmission X-ray topography was used for analyzing dislocation networks in as-grown web silicon. We were able to correlate minority carrier diffusion length with the configuration of the networks that are strongly affected by twin planes lying midway across the web thickness. Analysis of the networks is also useful in providing information regarding regions of high stress levels associated with a given growth environment.</jats:p

Comprehensive Model of Hydrogen Transport into a Solar Cell during Silicon Nitride Processing for Fire-Through Metallization

A mechanism for the transport of H into a Si solar cell during plasma-enhanced chemical vapor deposition (PECVD) of a hydrogenated silicon nitride (SiN:H) layer and its subsequent fire-through metallization process is described. The PECVD process generates process-induced traps, which ''store'' H at the surface of the solar cell. This stored H is released and diffuses rapidly into the bulk of Si during the high-temperature metallization-firing process. During the ramp-down, the diffused H associates with impurities and defects and passivates them. The firing step partially heals up the surface damage. The proposed model explains a variety of observations and experimental results

EFG Technology and Diagnostic R&D for Large-Scale PV Manufacturing: Annual Subcontract Report, 1 July 2003--30 June 2004

The objective of this subcontract over its duration was to carry out R&amp;D to advance RWE Schott Solar Inc. (formerly ASE Americas)--''RSSI''--manufacturing technology, processes and capabilities of wafer, cell, and module manufacturing lines, which will help configure them for scaling up of EFG ribbon technology to the 50-100 MW PV factory level. The basic EFG technology principles have already been established and are being demonstrated on the scale of 10-20 MW manufacturing lines. By the successful completion of this effort, RSSI is planning to reduce overhead costs of production and of direct, variable manufacturing costs with the scale up of EFG processes and equipment currently in use. To achieve these objectives, RSSI needs to maintain or enhance yield, quality, process control, and throughput relative to present levels throughout the three areas of wafer, cell, and module manufacture

PVMaT Cost Reductions in the EFG High-Volume PV Manufacturing Line: Annual Report, August 1998-December 2000

The PVMaT 5A2 program at ASE Americas is a three-year program that addresses topics in the development of manufacturing systems, low-cost processing approaches, and flexible manufacturing methods. The three-year objectives are as follows: (1) implementation of computer-aided manufacturing systems, including Statistical Process Control, to aid in electrical and mechanical yield improvements of 10%, (2) development and implementation of ISO 9000 and ISO 14000, (3) deployment of wafer production from large-diameter (up to 1 m) EFG cylinders and wafer thicknesses down to 95 microns, (4) development of low-damage, high-yield laser-cutting methods for thin wafers, (5) cell designs for &gt;15% cell efficiencies on 100-micron-thick EFG wafers, (6) development of Rapid Thermal Anneal processing for thin high-efficiency EFG cells, and (7) deployment of flexible manufacturing methods for diversification in wafer size and module design. In the second year of this program, the significant accomplishments in each of three tasks that cover these areas are as follows: Task 4-Manufacturing systems, Task 5-Low-cost processes, and Task 6-Flexible manufacturing

PVMaT cost reductions in the EFG high volume PV manufacturing line: Annual report, 5 August 1998--4 August 1999[PhotoVoltaic Manufacturing Technology, Edge-defined Film-fed Growth]

This report describes work performed by ASE Americas researchers during the first year of this Photovoltaic Manufacturing Technology 5A2 program. Significant accomplishments in each of three task are as follows. Task 1--Manufacturing Systems: Researchers completed key node analysis, started statistical process control (SPC) charting, carried out design-of-experiment (DoE) matrices on the cell line to optimize efficiencies, performed a capacity and bottleneck study, prepared a baseline chemical waste analysis report, and completed writing of more than 50% of documentation and statistical sections of ISO 9000 procedures. A highlight of this task is that cell efficiencies in manufacturing were increased by 0.4%--0.5% absolute, to an average in excess of 14.2%, with the help of DoE and SPC methods. Task 2--Low-Cost Processes: Researchers designed, constructed, and tested a 50-cm-diameter, edge-defined, film-fed growth (EFG) cylinder crystal growth system to successfully produce thin cylinders up to 1.2 meters in length; completed a model for heat transfer; successfully deployed new nozzle designs and used them with a laser wafer-cutting system with the potential to decrease cutting labor costs by 75% and capital costs by 2X; achieved laser-cutting speeds of up to 8X and evaluation of this system is proceeding in production; identified laser-cutting conditions that reduce damage for both Q-switched Nd:YAG and copper-vapor lasers with the help of a breakthrough in fundamental understanding of cutting with these short-pulse-length lasers; and found that bulk EFG material lifetimes are optimized when co-firing of silicon nitride and aluminum is carried out with rapid thermal processing (RTP). Task 3--Flexible Manufacturing: Researchers improved large-volume manufacturing of 10-cm {times} 15-cm EFG wafers by developing laser-cutting fixtures, adapting carriers and fabricating adjustable racks for etching and rinsing facilities, and installing a high-speed data collection net work; initiated fracture studies to develop methods to reduce wafer breakage; and started a module field studies program to collect data on field failures to help identify potential manufacturing problems. New encapsulants, which cure at room temperature, are being tested to improve flexibility and provide higher yields for thin wafers in lamination