Microcrystalline silicon for solar cells deposited at high rates by hot-wire CVD

Using two tungsten (W) filaments and a filament-substrate spacing of 3.2 cm, we have explored the deposition of microcrystalline silicon (muc-Si) solar cells, with the i-layer deposited at high deposition rates (R-d), by the hot-wire CVD (HWCVD) technique. These cells were deposited in the n-i-p configuration on textured stainless steel (SS) substrates, and all layers were deposited by HWCVD. Thin, highly crystalline seed layers were used to facilitate crystallite formation at the n-i interface. Companion devices were also fabricated on flat SS substrates, enabling structural measurements (by XRD) to be performed on i-layers used in actual device structures. Using a filament temperature of 1750 degreesC, device performance was explored as a function of i-layer deposition conditions, including variations in i-layer substrate temperature (T-sub) using constant H-2 dilution, and also variations in H, dilution during i-layer deposition. The intent of the latter is to affect crystallinity at the top surface of the i-layer (i-p interface). We report device performance resulting, from these studies, with all i-layers deposited at R-d > 5 Angstrom/s, and correlate them with i-layer structural studies. The highest device efficiency reported is 6.57%, which is a record efficiency for an all-hot-wire solar cell. (C) 2003 Elsevier Science B.V. All rights reserved.