Applied Surface Science, Vol.301, 51-55, 2014
Room temperature surface passivation of silicon for screen printed c-Si solar cells by HiTUS reactive sputter deposition
The dielectric coatings used on silicon solar cells serve a dual purpose: a surface passivation layer and as an antireflection coating. Silicon nitride films were deposited by sputtering, using a HiTUS technology, on crystalline silicon wafers. Films were deposited without substrate heating, which simplifies the deposition process, from a polycrystalline silicon target in a mixed ambient of argon, nitrogen and hydrogen gasses. After the deposition, the minority carrier lifetime, refractive index and deposition rate were measured. Photo conductance decay measurements show that the minority carrier lifetime increased up to 26 mu s on a 40 Omega/square doped 1 Omega cm p-type < 1 0 0 > Cz-Si pseudo square wafer (compared to 1 mu s measured for bare wafer) and up to 984 mu s for a double-side polished 3 Omega cm Cz-Si wafer (from similar to 70 mu s measured for uncoated wafer). Spectroscopic ellipsometry measurements showed that the refractive index of the deposited films was 2.05 at lambda = 632.8 nm; deposition rate was measured at 22.4 nm/min. The films were used to prepare screen-printed c-Si solar cells. The resultant cells showed an efficiency of 15.14% with silicon nitride films grown without the use of silane or substrate heating. (C) 2014 Elsevier B.V. All rights reserved.