Effects of hydrogen diluted silane plasma on amorphous silicon solar cells

We systematically studied amorphous silicon (a-Si:H) films and solar cells which were fabricated by H-2-diluted SiH4 plasma. The H-2 dilution improves the quality of poor materials resulting from non optimized pure SiH4 condi tions however this improvement can also be achieved by reducing the RF powe r under pure SiH4 conditions. The H-2 dilution is not always necessary for the optimization of a-Si:H. Higher diluted plasma reduces the optical absor ption coefficient of a-Si:H, resulting in a lower short circuit current (I- sc), and the H-2-dilution conditions could not give higher conversion effic iency (Eff) than the optimized pure SiH4 condition. The H-2-diluted plasma at a relatively low pressure (0.2 Torr) causes a lower open circuit voltage (V-oc) in spite of wider optical gaps and lower I-sc than values estimated from the optical absorption coefficient, probably due to the damage of und erlying layers by H ions or radicals. These plasma damages are suppressed b y increasing the pressure up to similar to 1.0 Torr.