Development of 22.5 % p-type tunnel oxide passivated contact solar cells through efficiency enhancement by replacing local Al-BSF in PERC cells with (p+) poly-Si/SiO2 carrier selective contact
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Choi, Wook-Jin (ORCID:000000032568419X)↗
Engineering topics
Min, Kwan Hong
Publications and source records attributed to Min, Kwan Hong.
Enhanced passivation and stability of negative charge injected SiN x with higher nitrogen content on the boron diffused surface of n-type Si solar cells
This paper explores the potential of the negatively charged SiN x using plasma charge injection technology to passivate the front textured boron-diffused emitter of n-type Si solar cells. The high-x value single SiN x layer with x ≥ 1.30 (x = N/Si) previously developed for the planarized rear-side passivation of p-type silicon solar cells, with an excellent passivation and charge stability, was found to be unacceptable for the passivation on the front textured boron emitter of n-type cells due to a severe bulk lifetime degradation issue. Therefore, in this study, we investigated a new concept of depositing a dual-x SiN x with a low-x SiN x layer (x~1.01) on top of a high-x SiN x layer (x~1.30) for passivation of the front textured rough surface of boron diffused emitter in n-type cells. Here, the optimized dual-x SiN x stack reveals the promise of charge retention for more than 25 years in field operation as well as excellent passivation of boron-doped emitter without bulk lifetime degradation. N-type cells with the optimized dual-x SiN x after charge injection show comparable cell performance to Al 2 O 3 passivated reference cells. The results of cell-level light stability tests using one-cell minimodules exhibit cell performance decay characteristics similar to the traditional Al 2 O 3 /SiN x passivated reference module.
14 SOLAR ENERGY↗
Comparison of passivation properties of plasma-assisted ALD and APCVD deposited Al 2 O 3 with SiN x capping
In this paper, we report on the direct comparison of Al 2 O 3 films deposited by plasma-assisted atomic layer deposition (ALD) and atmospheric pressure chemical vapor deposition (APCVD) techniques on the passivation properties of both bare and boron diffused Si surfaces. It is found that ALD and APCVD deposited Al 2 O 3 layers with SiN x capping have very similar chemical composition, hydrogen concentration at the Al 2 O 3 /Si interface, and interface defect density (D it ), but the ALD film has slightly higher negative fixed charge (Q f ) after a high temperature (~750 °C) contact firing cycle typically used for solar cell fabrication. Both films showed excellent surface recombination velocities of <5 cm/s on planar and textured un-diffused Si wafers, but the ALD films gave 1 to 8 fA/cm 2 lower emitter saturation current densities (J 0e ) on implanted boron emitters with sheet resistance in the range of 90–180 Ω/. This is attributed to the observed slightly higher negative charge-induced field-effect passivation in the ALD films. However, SiN x /Al 2 O 3 /p + /n/n + passivated emitter rear totally diffused (PERT) cell structures fabricated with 110 and 150 Ω/ emitter in this study showed no appreciable difference in cell efficiency. Device analysis and simulations showed that even for >23% high-performance solar cells design, with very low bulk and rear contact recombination, the observed small difference in J 0e has negligible effect on cell efficiency. Furthermore, APCVD Al 2 O 3 passivation of B emitter can produce comparable efficiencies to their counterpart ALD Al 2 O 3 passivated n-type Si solar cells.
14 SOLAR ENERGY↗