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21.0%‐efficient co‐diffused screen printed n‐type silicon solar cell with rear‐side boron emitter
Author(s) -
Wehmeier Nadine,
Lim Bianca,
Nowack Anja,
Schmidt Jan,
Dullweber Thorsten,
Brendel Rolf
Publication year - 2016
Publication title -
physica status solidi (rrl) – rapid research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.786
H-Index - 68
eISSN - 1862-6270
pISSN - 1862-6254
DOI - 10.1002/pssr.201510393
Subject(s) - plasma enhanced chemical vapor deposition , boron , common emitter , diborane , silane , materials science , silicon , solar cell , saturation current , diffusion , analytical chemistry (journal) , chemical vapor deposition , chemistry , optoelectronics , electrical engineering , composite material , physics , organic chemistry , voltage , thermodynamics , engineering , chromatography
Plasma enhanced chemical vapor deposition (PECVD) is applied to deposit boron silicate glasses (BSG) acting as boron diffusion source during the fabrication of n‐type silicon solar cells. We characterize the resulting boron‐diffused emitter after boron drive‐in from PECVD BSG by measuring the sheet resistances R sheet,B and saturation current densities J 0,B . For process optimization, we vary the PECVD deposition parameters such as the gas flows of the precursor gases silane and diborane and the PECVD BSG layer thickness. We find an optimum gas flow ratio of SiH 4 /B 2 H 6 = 8% and layer thickness of 40 nm. After boron drive in from these PECVD BSG diffusion sources, a low J 0,B values of 21 fA/cm 2 is reached for R sheet,B = 70 Ω/□. The optimized PECVD BSG layers together with a co‐diffusion process are implemented into the fabrication process of passivated emitter and rear totally diffused (PERT) back junction (BJ) cells on n‐type silicon. An independently confirmed energy conversion efficiency of 21.0% is achieved on 15.6 × 15.6 cm 2 cell area with a simplified process flow. This is the highest efficiency reported for a co‐diffused n‐type PERT BJ cell using PECVD BSG as diffusion source. A loss analysis shows a small contribution of 0.13 mW/cm 2 of the boron diffusion to the recombination loss proving the high quality of this diffusion source. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)