|Effect of Al Content on the Performance of Ag/Al Screen Printed N-type Si Solar cells|
|Young Woo Ok1, Ajay D. Upadhyaya1, Francesco Zimbardi1, Yuguo Tao1, Ian B. Copper1, Ajeet Rohatgi1, Alan F. Carroll2, Terry Suess2
1Georgia Institute of Technology, Atlanta, GA, United States
/2Dupont Microcircuit Materials, Research Triangle Park, NC, United States
In this paper, the role of Al content in Ag/Al paste for making screen printed contacts to B emitter is investigated. Four different pastes with <5% Al were formulated. (Al ratio Paste A>B>C>D). It is found that contact resistance decreased monotonically with the increase in Al content. In addition, a slight decrease in effective sheet resistance of boron emitter was observed for higher Al content paste, possibly due to some Al incorporation underneath the grid line. These two effects resulted in an increase in fill factor for higher Al content paste. However, increased Al content also resulted in higher emitter saturation current density (J0e), resulting in a slight decrease in Voc. The competition between the fill factor and J0e led to an optimum Al contents (Paste B), which produced a cell efficiency of 19.2% for a basic n-type front junction cell.