Efficient silicon nitride SiNx:H antireflective and passivation layers deposited by atmospheric pressure PECVD for silicon solar cells

• Published in: Progress in photovoltaics Vol. 27; no. 11; pp. 1007 - 1019
• Main Authors: Lelièvre, Jean‐François, Kafle, Bishal, Saint‐Cast, Pierre, Brunet, Paul, Magnan, Romain, Hernandez, Emmanuel, Pouliquen, Sylvain, Massines, Françoise
• Format: Journal Article
• Language: English
• Published: Bognor Regis Wiley Subscription Services, Inc 01-11-2019
• Subjects: Absorptivity; Amplitude modulation; Antireflection coatings; antireflective coating; Atmospheric pressure; atmospheric pressure PECVD; Capping; Dielectric barrier discharge; Emitters; hydrogenated silicon nitride SiNx:H; Optical properties; Optimization; Organic chemistry; passivation layer; Passivity; PERC solar cells; Photovoltaic cells; Plasma; Plasma enhanced chemical vapor deposition; Plasma jets; Refractivity; Silicon nitride; Silicon substrates; Solar cells; Thermal stability; Thin films
• ISSN: 1062-7995; 1099-159X
• DOI: 10.1002/pip.3141

This work demonstrates the efficient optical and passivation properties provided by hydrogenated silicon nitride (SiNx:H) layers deposited in a lab‐scale atmospheric pressure plasma enhanced chemical vapor deposition (AP‐PECVD) reactor. By applying modulated low‐frequency plasma (200 kHz), homogeneous SiNx:H layers, with small variances in thickness w and refractive index n (Δw ≤ 2 nm; Δn ≤ 0.02), were achieved on a surface area of 45 × 55 mm2. The use of voltage amplitude modulation enabled discharge optimization and led to greatly enhanced SiNx:H film homogeneity and conformity in comparison with continuous plasma discharge conditions. Additionally, AP‐PECVD SiNx:H showed good thermal stability (Δw ≤ 1 nm; Δn ≤ −0.02) with low absorption coefficients (k ≤ 0.1 at 275 nm), demonstrating that such layers could act as efficient antireflective coatings. Furthermore, outstanding surface passivation properties were achieved after firing, both on n‐type FZ c‐Si substrates of standard 2.8 Ω.cm doping (τeff = 1.45 ms) and on highly doped 85 Ω/sq n+ emitters (j0e = 74 ± 2 fA.cm−2). Finally, AP‐PECVD SiNx:H thin films were tested on industrial passivated emitter and rear solar cell (PERC) architectures, where the potential of applying these layers both as efficient rear‐side capping layer and front‐side antireflective coating was demonstrated. The first lab‐scale 40 × 40 mm2 PERC solar cells featuring AP‐PECVD SiNx:H layers led to conversion efficiencies of up to 20.6%. These results pave the way for upscaling the dielectric barrier discharge lab‐scale reactor in an industrial in‐line process, which could provide low‐cost and high‐throughput SiNx:H capping and antireflective layers.
For the first time, atmospheric pressure PECVD process was successfully applied for the realization of high efficiency PERC solar cells. The direct correlation between plasma modulation parameters and the optical and passivating properties of AP‐PECVD SiNx thin films was studied in detail. The best AP‐PECVD SiNx coatings were successfully integrated in PERC structures demonstrating efficient properties both as rear side capping layer and as front side antireflective and passivation layer.