Light induced degradation in nanocrystalline Si films and related solar cells: Role of crystalline fraction

Silicon thin films with different crystalline volume fractions have been deposited at different power and pressure conditions. Structural properties of the films have been investigated. The effects of crystalline volume fractions and grain sizes on the degradation of photoconductivity have been studied. Single-junction solar cells have been fabricated with protocrystalline and nanocrystalline Si as absorber layer. Protocrystalline silicon solar cells show less than 1% degradation upto 50 h of light soaking. Then the cells degrade upto 500 h and thereafter become steady. Nanocrystalline solar cells show degradation initially and become steady after 10 h of light soaking. Using protocrystalline silicon as absorber layer the solar cell efficiency degrades 9% before stabilization, whereas using nanocrystalline silicon as absorber layer (Xc∼65%) the solar cell efficiency degrades 2.9%. Stabilized efficiency of the second type of cell is better than that of the first cell, but initial efficiency is higher for the first cell (η=7.1%).