Jalal Salami

Application of a boron source diffusion barrier for the fabrication of back contact silicon solar cells

Interdigitated back contact and emitter wrap-through solar cells were fabricated using a diffusion barrier to achieve selective phosphorus diffusion for the patterning of the base and the emitter regions on the cell rear. The addition of boron to the diffusion barrier for emitter formation in the underlying n-type base and for the formation of a back surface field in the case of a p-type base was further examined. Boron was successfully incorporated into the n-type Si for the creation of rear p/sup +/ emitters in an interdigitated back contact cell. An order of magnitude improvement in the surface recombination velocity to 10/sup 3/ cm/s could be achieved with a p/sup +/ surface field applied to the base of p-type wafers. Incorporating this technology, best multi-crystalline emitter wrap-through cell performance could be gained with a 1k-2k /spl Omega///spl square/ surface field; however, the characteristics were rapidly dominated by increased saturation current as the surface field layer concentration was increased.

Diffusion Paste Development for Printable IBC and Bifacial Silicon Solar Cells

Increasing cell efficiency and lowering the cost of solar cell manufacturing is a continuous challenge in solar cell industries. Higher efficiency concepts like interdigitated back contact (IBC), and bifacial cells, with using thinner silicon solar cells are ways to reduce the total solar cell manufacturing cost. Typically the high efficiency concepts require costly extra processing steps. Developing the proper paste for printing application of high efficiency concepts could make these designs cost effective and easily manufactured. These pastes can be printable in a continuous manner using processes like screen printing or ink jet printing. This paper describes newly developed low cost phosphorous, boron, and diffusion barrier pastes. It shows the characterization of the newly developed phosphorous paste (99-038), boron paste (99-033), and diffusion barrier paste (99-001). These low cost pastes can easily be printed and make high efficiency concept cell designs a low cost reality. Characteristic features of sheet resistance, junction depth and minority carrier lifetime is discussed

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.