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

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Abstract

Abstract This work demonstrates the efficient optical and passivation properties provided by hydrogenated silicon nitride (SiN x :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 SiN x :H layers, with small variances in thickness w and refractive index n (Δ w ≤ 2 nm; Δ n ≤ 0.02), were achieved on a surface area of 45 × 55 mm 2 . The use of voltage amplitude modulation enabled discharge optimization and led to greatly enhanced SiN x :H film homogeneity and conformity in comparison with continuous plasma discharge conditions. Additionally, AP‐PECVD SiN x :H showed good thermal stability (Δ w ≤ 1 nm; Δ n ≤ −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 ( τ eff = 1.45 ms) and on highly doped 85 Ω/sq n + emitters ( j 0e = 74 ± 2 fA.cm −2 ). Finally, AP‐PECVD SiN x :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 mm 2 PERC solar cells featuring AP‐PECVD SiN x :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 SiN x :H capping and antireflective layers.

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