Regulation to Ag–Al spikes through silver aluminum paste with Al–Si alloy

Abstract

It is known that metallization of Ag–Al pastes to boron doped emitter of N-type solar cells will reduce contact resistance, because Al will promote forming Ag–Al spikes, providing conductive channels. However, deeper Ag–Al spikes will exacerbate metal recombination and deteriorate cell performance, thus requiring regulation. It has been reported that adding Si to Ag–Al pastes could effectively limit the formation of Ag–Al spikes, but it will increase grid line resistance and reduce conductivity. Based on this, we prepared new Ag–Al pastes using Al–Si alloys, which effectively regulated Ag–Al spikes and ensured electrical properties. In addition, we comprehensively compared the contact properties of conventional Ag–Al pastes, Ag–Al pastes with added Si, and Al–Si alloy pastes. The results indicated that conventional Ag–Al pastes have lower contact potential barriers and better contact performance, but Ag–Al spikes are difficult to control. Adding Si to Ag–Al pastes effectively limited the formation of spikes, but it will significantly increase potential barriers and deteriorate electrical performance. By contrast, using Al–Si alloys can not only achieve comprehensive regulation of the size and composition of Ag–Al spikes, but also ensure good electrical performance. This study developed Al–Si alloy pastes with great potential for application, which were of great significance for regulation of Ag–Al spikes and the development of advanced Ag–Al pastes.