Silicon Photovoltaics
Twenty highly trained technicians and researchers work in ECN’s group Silicon Photovoltaics. We aim to make silicon wafer-based photovoltaics cheaper by increasing efficiency and by reducing silicon usage in grams per watt-peak of module power. Our focus is on large-scale inline production processes. We work in national projects financed by SenterNovem, in EU funded projects, and privately funded projects.
Process development for large-scale production of 17% multi-crystalline silicon cells
New and adapted processes have been developed to make solar cells with 16% efficiency on average in our pilot line. Our speciality is the development of a fully inline production concept to minimize handling of the solar cells. ECN has been the first to reach 17% maximum efficiency on standard multi-crystalline silicon with such industrial inline processing.
traditional etch + anti-reflection coating
texture etch +anti-reflection coating
Inline texture etching of wire-sawn silicon wafers.
Specifically, we have developed an inline texture etch, which leads to 6% higher current compared to alkaline etched cells. Together with Roth&Rau, an inline PECVD has been developed for optimal bulk and surface passivation by depositing optimal silicon nitride layers. Both inline etching and inline PECVD are used by the PV industry.
First prototype inline PECVD developed by Roth & Rau and ECN.
Prototype inline etcher.
Direct casting of silicon wafers for solar cells
ECN develops the “Ribbon Growth on Substrate” (RGS) technology for direct casting of silicon wafers. The advantage of RGS is that wafers are cast directly from the molten silicon whereas traditional wafers are cut from blocks of crystallised silicon. Therefore, RGS consumes three times less silicon per wafer than needed for sawn wafers including losses due to ingot crystallisation, block cutting and wire sawing. RGS has the potential to yield 1 wafer per second, which corresponds to enough ribbons for 50 mega watt-peak per year of solar cell production. In 2000, ECN continued the RGS technology development started by Bayer in 1986. Since then, the efficiency with a standard industrial process has been increased from 8% to 13.3% in 2005. Also, the design of a full-scale prototype has been finalised. The construction of the prototype was started in 2005 and first ribbons will be produced on this machine in 2007.
First thin RGS wafer (111 micrometer).
Characterisation of silicon feedstock and wafers
ECN leads the SOLSILC team to develop the direct carbothermic reduction of high-purity quartz and carbon black to produce solar grade silicon. ECN has established specifications and measuring techniques to validate feedstock and wafers. Quantities that qualify the material for high-efficiency cells are the oxygen content and the minority carrier lifetime after phosphorous gettering.
Research production of solar grade silicon (SOLSILC project).
Contact person: Dr. J.H. Bultman
Tel.no. +31 224 56 4786
bultman@ecn.nl
