Influence of Emitter Properties on Contact Formation to P+ Silicon

Impact of boron doping profiles on the specific contact resistance of screen printed Ag–Al contacts on silicon

“…However, the latter is not further considered within this work as results from Hoenig [26] emphasize that current transport via direct silicon-silver contacts is more likely for phosphorusdoped emitters and silver contacts, which is supported by results of Cabrera et al [23]. Additionally, Fritz et al [14] also propose the direct current conduction between Ag-Al contact and borondoped silicon as being more likely to occur than other current transport mechanisms. Furthermore, results published by Heinz et al [3] show the crystallites formed below an Ag-Al paste on a boron-doped surface consist almost solely of silver.…”

“…consistent with literature, Boltzmann statistics is used in the following to calculate E F at room temperature according to Eq. (14) using N V ¼ 2.503 Á 10 19 cm À 3 (see the Appendix). 7)] processes very well for N 410 18 cm À 3 .…”

“…On the other hand, a higher Al content in the paste leads to increased charge carrier recombination in the metallized areas and thus to larger metallization-induced voltage losses [3]. For Ag-Al pastes and boron emitters, Fritz et al report that, apart from the maximum charge carrier concentration N max , also other emitter properties-like their doping profile shapes or the defect concentration at the emitter surface-possibly play a decisive role for achieving low ρ C [14]. From two different boron emitters investigated in their studies, surprisingly the emitter with the lower N max yields the lower ρ C , contradicting the theory of ideal planar contacts.…”

Formation of Ag/Al Screen-Printing Contacts on B Emitters

“…Contacting p + Si with Ag screen-printing pastes can lead to specific contact resistances c above 50 mΩ · cm 2 [1]- [4], which is rather poor compared with Ag-based contacts to phosphorous-doped n + Si layers exhibiting c typically below 5 mΩ · cm 2 [5]. For BBr 3 -based B emitters similar to the ones used in this study, a specific contact resistance above 20 mΩ · cm 2 has been reported [6]. The addition of Al to the paste leads to a lower c , as was first shown by Kopecek et al [2].…”

Passivating boron silicate glasses for co-diffused high-efficiency n-type silicon solar cell application

“…Until now, it was not possible to reach the same low level of contact resistivity using Ag instead of Ag/Al pastes to contact B emitters with or without established surface passivation layers. 14,15 All presented SiO x :B and SiN x layers are deposited in a single chamber, inductively coupled plasma plasmaenhanced chemical vapor deposition (ICP-PECVD) lab-tool. The lab-tool displays direct as well as remote plasma characteristics for high-density films.…”