The degradation properties of a-Si:H films prepared by less-conventional methods [solar cells]

Light-induced degradation properties of a-Si:H solar cell films prepared by VHF high growth rate PECVD, thermally expanding plasma, and a-Si:D are investigated using nanosecond pulse laser exposures and the measurements of photoconductivity, subgap absorption, and ESR. The light-induced defect creation kinetics is similar in all films and obeys a time power-law independent of the initial defect concentration. The degradation of photoconductive properties is governed by the creation of defects with different capture coefficients. The capture coefficients have similar values in most of a-Si:H solar cell films but depend strongly on the temperature at which the defects are created. In contrast, the capture coefficients for defects in a-Si:D are considerably smaller suggesting a possible difference in electron-phonon coupling. Structural changes around the defect and their modification at various temperatures are suggested to affect the defect capture coefficients.