Integration of expanding thermal plasma deposited hydrogenated amorphous silicon in solar cells

A cascaded arc expanding thermal plasma is used to deposit intrinsic hydrogenated amorphous silicon at growth rates larger than 2 Å/s. Implementation into a single junction p-i-n solar cell resulted in initial efficiencies of ~7%, although all the optical and initial electrical properties of the individual layers are comparable with RF-PECVD deposited films. The somewhat lower efficiency is due to a smaller fill factor. Spectral response measurements, illuminated J,V- measurements, and simulations indicate that a higher local defect density in the region near the p-i interface might be responsible for the smaller fill factor in comparison with conventional low- rate RF-PECVD. The higher defect density is most likely caused by the initial growth in the first 10 to 50 nm. Therefore, controlled initial growth of the intrinsic layer is suggested for good solar cell performance.