Optimized amorphous silicon nitride layers for the front side passivation of c-Si PERC solar cells

• Published in: EPJ Photovoltaics 2020, Vol.11, p.6
• Main Authors: Mohamed Okasha Mohamed Okasha, Asmaa, Kafle, Bishal, Torda, Benjamin, Teßmann, Christopher, Hofmann, Marc
• Format: Article
• Language: English
• Subjects: Ammonia; Amorphous materials; Amorphous silicon; Antireflection coatings; Arc deposition; Chambers; Circuits; Electrical properties; Emitters; Endangered & extinct species; Fourier transforms; Hydrogen bonds; Optical properties; passivation; Passivity; pecvd; perc cells; Photovoltaic cells; Plasma enhanced chemical vapor deposition; Plasma etching; Quantum efficiency; Short circuit currents; Silicon nitride; Solar cells; Spectrum analysis; Substrates
• ISSN: 2105-0716; 2105-0716
• DOI: 10.1051/epjpv/2020003

Plasma-enhanced chemical vapour deposition (PECVD) SiN x is the typical choice as anti-reflection coating (ARC) for Silicon based solar cells. However, there still exists a room for improvement in passivation quality of SiN x while maintaining good optics for the front side of a solar cell. In this paper, we studied in detail the optical and electrical properties of SiN x layers by varying the chamber pressure and substrate temperature in an industrially used inline PECVD tool. Both the optical as well as electrical properties of SiN x layers were found to be significantly influenced by the chamber pressure and substrate temperature. A trade-off between excellent optics and low surface recombination is observed with an increase in chamber pressure, whereas higher substrate temperature generally led to better passivation quality. The Si-H bond density, which is expected to directly influence the quality of surface passivation, increased at high pressure and at low substrate temperature. Based on our investigations, a good compromise between optics and surface passivation is struck to prepare optimized SiN x layers and apply them as passivation layers for the front side of passivated emitter and rear cell (PERC) solar cells. The best solar cells show high short-circuit current density ( j SC ) of 39.9 mA/cm 2 corresponding to the SiN x layers with low parasitic absorption, good antireflection property, and excellent passivation of the surface and bulk silicon. The current-voltage (I-V) results are found to be in agreement with internal quantum efficiency (IQE) measurements of the solar cells.