Abstract
A kind of low recombination firing-through screen-printing aluminum (Al) paste is proposed in this work to be used for a boron-diffused N-type solar cell front side metallization. A front side fire-through contact (FTC) approach has been carried out for the formation of local contacts for a front surface passivated solar cell. With a low contact resistivity (ρc) of 1.0 mΩ·cm2, good ohmic contact between the boron-doped front surface of the silicon sample and the Al paste was realized. To obtain a good energy conversion efficiency, a balance can be achieved between the open circuit voltage (Voc) and contact resistivity (ρc) of the cell by combining suitable Al powders and appropriate additives. The detailed micro-contact difference in Si/metallization between the firing-through Al paste and silver-aluminum (Ag-Al) paste was analyzed. The dark saturation current density beneath the metal contact (J0, metal) of the Si/metallization region using our firing-through Al paste was discussed, which was proven to be 61% lower than using Ag-Al paste. The pseudo energy conversion efficiency of the cell using Al paste measured by Suns-VOC was also higher than using Ag-Al paste. The role of Al paste in low surface metal recombination is discussed. The utilization of this new kind of Al paste was much cheaper and more convenient, compared to the traditional process using Ag or Ag-Al paste.
Highlights
Accepted: 2 February 2021Over recent decades, silicon (Si) solar cells have been widely used in various lighting and power generation systems
A passivated emitter and rear cell (PERC) based on P-type Czochralski-grown silicon (CzSi) substrate has been introduced into production [1]
There is no doubt that the metallization process forming the electrode has turned out to be an important part of the enhancement of energy conversion efficiency, which adopts screen-printing paste composed of metal particles, low-melting glass frits and an organic part
Summary
Silicon (Si) solar cells have been widely used in various lighting and power generation systems. Aluminum conductive paste has become an important material for the back side metallization in the formation of the back surface field (BSF) in P-type silicon solar cells [29,30,31]. In this case, the charge carrier’s lifetime could be significantly prolonged. The investigation of the contact mechanism between the Al paste and Si wafer has been carried out through micro-structure analysis at the Si/metallization interface Both the Al powder and the additive of the Al paste were checked to understand the formation process of ohmic contact on the front side metallization for the silicon solar cell. Compared with the traditional process by using Ag or Ag-Al paste for the boron-doped emitter, it is much cheaper and more convenient using Al paste, which is instructive and significant for the current transmission mechanism of Si/metallization and improved application of Al conduction pastes
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