Metallisation of Boron‐Doped Polysilicon Layers by Screen Printed Silver Pastes

Abstract

In this work, we report on hole selective passivating contacts, which consist of a SiOx tunnel layer and an in situ boron‐doped 300 nm thick p+ polysilicon layer deposited by LPCVD. Using a SiNx:H capping layer, we show an extremely low dark saturation current density J0 of 1 fA cm−2 after contact firing. At the same time, we demonstrate that commercially available and screen‐printed fire through Ag pastes are capable of contacting the p+ polysilicon layer, with minimum contact resistance ρc = 2 mΩ cm2. We do find increased interface recombination below the metal contacts of around 250 fA cm−2, which represents a considerable advance compared to conventional screen printed metallisation on diffused junctions.

Integrating transparent conductive oxides to improve the infrared response of silicon solar cells with passivating rear contacts

“…to < 22% for bifacial cells on 6" Cz wafers in [4]). In essence, LPCVD poly-Si contacts contacted by fire-through metallization become locally depassivated, due to the penetration of metal through the polySi layer into the c-Si absorber (J 0,met » J 0,pass [5,6]). Reasonable J 0,met and contact resistivity (ρ c ) values can be achieved for heavily-doped, thick poly-Si films, but here the IR response is reduced noticeably due to free carrier absorption (FCA).…”

26.1%‐efficient POLO‐IBC cells: Quantification of electrical and optical loss mechanisms

“…In previous studies, we already achieved values down to 0.6 fA cm −2 for n POLO junctions and down to 3.8 fA cm −2 for p POLO junctions . Other groups even reported values down to 1 fA cm −2 for p POLO after hydrogenation with an optimized firing process . Because it is difficult to predict exactly how far the passivation quality of the POLO junctions can be improved, we calculate the efficiency potential of our cells for the limiting case of perfect surface passivation and negligible series resistance effects (ie, exclusively optical limitations).…”

“…28 Other groups even reported values down to 1 fA cm −2 for pPOLO after hydrogenation with an optimized firing process. 29 Because it is difficult to predict exactly how far the passivation quality of the POLO junctions can be improved, we calculate the efficiency potential of our cells for the lim- The open symbols in Figure 5 show the reflectance R exp of the POLO-IBC cell that we measure with a spectrophotometer. We apply The blue dashed line in Figure 5 symbolizes R f (λ).…”

P‐Type Silicon Solar Cells with Passivating Rear Contact Formed by LPCVD p+ Polysilicon and Screen Printed Ag Metallization

“…As was shown in an earlier paper, screen printed Ag pastes allow for a low contact resistance to boron doped polysilicon layers and a contact recombination J 0,met similar to that of local Al alloyed rear contact in PERC solar cells . Thus, we apply the same Ag paste in a grid layout with either five or zero busbars, that is, only fingers (denoted “5BB” or “0BB,” respectively), for contacting both the front and rear of our device, which removes one printing and drying step compared to PERC solar cells as well as the laser process for local contact opening.…”