Researchers from the Ecole Polytechnique Fédérale de Lausanne (EPFL) have suggested combining the two high temperature steps that are used in producing tunnel oxide-passivated contact (topcon) solar cells in a single coanneel process. The first results show promising results in the drilling concentration, passion quality and contact resistance.
A research team led by the EPFL of Switzerland has tried to simplify the production of top con cells of the Topcon by combining the two required steps with high temperature-front-emitter formation and rear passivating contact manufacturing-in a single process.
The first process consists of depositing a borosilicate glass (BSG) layer in the cell, while the second step spread Borosilicate of the BSG in the waffle.
“We have investigated the Front Boron Emitter formation process larger, aimed at the co-annealing process,” said researcher Thibault Schaller PV -Magazine. ‘Building on the knowledge of earlier experiments, we have introduced a drive-in step in an oxygen environment in the coining process, initially only carried out in an air environment. With the introduction of this drive-in-step, we have succeeded in reducing recombination losses in the emitter and making it more compatible with standard industrial metallization approaches. “
Schaller said that the rear passivating contact showed promising compatibility with the optimized co-annealing process. He added that the team wants to demonstrate that co-concept co-amnated topcon devices of more than 24% efficiency in the laboratory, noticing that the streamlined process could lower the return times of the energy and, above all, beneficial in countries with high facilities and equipment costs.
The proposed hybrid process is a “low-fat production” process for co-user people, whereby the front and rear doped layers are subsequently deposited by plasma-improved chemical vapor deposits (PECVD). The Co-Verancuning Stap is then carried out to form the front emitter and to activate the rear passion contact.
Image: EPFL, Solar energy materials and solar cells, CC by 4.0
“Based on the acquired knowledge, we are changing the co-anning step by adding a drive-in phase that is carried out in an O2 environment to reduce the surface concentration and increase the emitter depth,” the researchers said.
A series of reviews and a feasibility analysis showed that the proposed two-step co-verancun process helps to effectively reduce the surface concentration and to increase the depth of emitters that diffunded from a plasma-defined borosilicate diffusion source.
Through the single process, the academics reached an emitter profile with a surface concentration of 2.2 x 1019 cm-3 And an emitter depth of 880 Nm, of which they said it is fully compatible with standard industrial metallization obtained by screen prints and shooting through silver (AG) or aluminum (already) metallization pastas.
The analysis, however, also showed that the quality of passivation after co-anals was not uniform.
“We show that although this modification reduces surface concentration and increases the emitter depth, resulting in a reduced surface area recomination and improved compatibility with standard industrial metallization processes,” the researchers also stated and noticed that the new production costs is usually intended to reduce the top concel of the top concel of the top concel.
Although the new process seems to offer good results in terms of drilling concentration profile, passion quality and contact resistance, the scientists said that further optimization is required.
The new production process was presented in the study “Drill-emitter development for Topcon C-Si solar cells based on plasma-drawn board differential source and poly-si (s) passivating contact“Published in Solar energy materials and solar cells.
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