Erik Sauar

Hydrogen Release and Defect Formation During Heat Treatments of SiNx:H/a-Si: H Double Passivation Layer on C-SI Substrate

The quality and temperature stability of surface passivation of silicon by a double layer consisting of a hydrogenated amorphous silicon thin film capped by a silicon nitride anti-reflection coating are studied. It is established that the passivation effect of the double layer can be significantly enhanced after short annealing for temperatures up to about 500degC, whereas annealing at higher temperatures results in degradation of the passivation properties. It is found that the increased effective recombination lifetime after annealing at temperatures below 500degC results from hydrogen redistribution in the interface region. Furthermore, presence of interfacial structural defects formed due to hydrogen release at temperatures around 600degC, is believed to be the cause of the lifetime decrease after heat treatments at higher temperatures

Interactions Between Metals and Different Grain Boundary Types and Their Impact on Multicrystalline Silicon Device Performance

The mechanical and electrical properties of polycrystalline solids, such as metals, ceramics, and photovoltaic-grade multicrystalline silicon (mc-Si), are strongly regulated by the interactions between impurities and grain boundaries. In this broader context, we combine synchrotron-based X-ray fluorescence microscopy (mu-XRF), SEM-based electron back-scatter diffraction (EBSD), and conventional techniques to correlate metal precipitation behavior with grain boundary character (type), electrical activity, and microstructure in commercial multicrystalline silicon (mc-Si) materials. It is directly observed that metals tend to form precipitates selectively at higher-Sigma coincidence site lattice (CSL) boundaries and non-CSL boundaries, while largely avoiding precipitation at Sigma3 boundaries, and to a lesser extent, Sigma9. The electrical impacts of this behavior differ, depending on surrounding intragranular quality. A discussion of mc-Si grain boundary engineering ensues

Hot-melt screen-printing of front contacts on crystalline silicon solar cells

This work describes a study of hot-melt (HM) screen-printing of front contacts as a function of print speed, print table temperature, squeegee temperature, paste composition and firing profiles. The results presented here will show that it is possible to print lines with higher aspect ratio compared with standard screen-printing. Optimum parameters for printing seems to be high print speed in combination high squeegee temperature. There is a trade off between the height and width of the finger lines when adjusting the table temperature. Firing with fingers facing down at high belt speeds results in shrinking of line width between 15% and 20%. At present, the best efficiency results from HM screen-printing are at par with standard printed solar cells.

A path towards low-cost crystalline silicon PV

In 2005 REC developed its 5 year cost and technology roadmap for the manufacturing of photovoltaic modules based on multi crystalline silicon wafers. The roadmap estimated the combined cost impact of a new silicon manufacturing process, thinner wafers, thinner sawing wire, higher crystal quality, new cell process with higher cell efficiency as well as scale up, improved manufacturing equipment, continuous improvements in operation and automation of multiple process steps. Our conclusion was that the manufacturing cost of crystalline silicon PV modules could be reduced by almost 50% in 2010 compared to what we regarded as world class manufacturing cost in 2005 if all developments were successful. Current development status in 2008 indicates that the 2010 roadmap is reachable.