Multi-crystalline si solar cells with very fast deposited (108 nm/min) passivating hot wire CVD silicon nitride as antireflection coating

Hot-wire chemical vapor deposition (HWCVD) is a promising technique for very fast deposition of high quality thin films. We developed processing conditions for device quality silicon nitride (a-SiNx:H) anti-reflection coating (ARC) at high deposition rates of 3 nm/s. The HWCVD SiNx layers were deposited on multicrystalline silicon (mc-Si) solar cells provided by IMEC and ECN Solar Energy. Reference cells were provided with optimized parallel plate PECVD SiNx and microwave PECVD SiNx respectively. The application of HWCVD SiNx on IMEC mc-Si solar cells led to effective passivation, evidenced by a V-oc of 606 m V and consistent IQE curves. For further optimization, series were made with HW SiNx (with different x) on mc-Si solar cells from ECN Solar Energy. The best cell efficiencies were obtained for samples with a N/Si ratio of 1.2 and a high mass density of >2.9g/cm(3). The best solar cells reached an efficiency of 15.7%, which is similar to the best reference cell, made from neighboring wafers, with microwave PECVD SiNx. The IQE measurements and high Voc values for these cells with HW SiNx demonstrate good bulk passivation. PC1D simulations confirm the excellent bulk- and surface-passivation for HW SiNx coatings. Interesting is the significantly higher blue response for the cells with HWCVD SiNx when compared to the PECVD SiNx reference cells. This difference in blue response is caused by lower light absorption of the HWCVD layers (compared to microwave CVD; ECN) and better surface passivation (compared to parallel plate PECVD; IMEC). The application of HW SiNx as a passivating antireflection layer on mc-Si solar cells leads to efficiencies comparable to those with optimized PECVD SiNx coatings, although HWCVD is performed at a much higher deposition rate. Copyright (C) 2007 John Wiley & Sons, Ltd.