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Rapidly deposited hote-wire cvd silicon nitride as high-quality passivating anti-reflection coating on (multi-)crystaline si solar cells
Verlaan, V.; Werf, C.H.M. van der; Houweling, Z.S.; Mai, Y; Bakker, R.; Romijn, I.G.; Weeber, A.W.; Goldbach, H.D.; Schropp, R.E.I.
Gepubliceerd door: Publicatie datum:
ECN Zonne-energie 21-6-2007
ECN publicatienummer: Publicatie type:
ECN-M--07-060 Conferentiebijdrage
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Gepresenteerd op: SAFE 2007, , Malta, 25-27 juni 2007.

Hot-wire chemical vapor deposition (HWCVD) is a promising technique for very fast deposition of high quality thin films. We investigated silicon nitride (SiNx) deposited with HWCVD as passivating antireflection coating (ARC) at a high deposition rate of 180 nm/min. Series of multi-crystalline silicon (mc-Si) solar cells were made using HWCVD SiNx with different atomic compositions. The open circuit voltage (Voc) and the short circuit current density (Jsc) have an optimum at an N/Si ratio (x) of 1.31. At this composition, the best solar cells reached an efficiency of 15.7 %, close to the best reference cell with optimized microwave PECVD SiNx (16.1%). The optimum at N/Si = 1.31 is explained by the high mass density, which peaks at this composition. Internal Quantum Efficiency (IQE) measurements at 1000 nm confirm this optimum and prove good bulk passivation. The IQE at a wavelength of 400 nm shows a combined optimal effect of surface passivation and absorption. The optimal N/Si ratio of 1.31 is significantly higher than the values reported for PECVD coatings (1.0). This higher N/Si ratio for HWCVD films leads to a larger bandgap and thus lower light absorption. Consequently, a higher IQE blue response and a slightly higher Jsc are obtained with HWCVD SiNx coatings.

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