Effect of gas flow rates on PECVD-deposited nanocrystalline silicon thin film and solar cell properties

Nanocrystalline silicon films have been deposited at a plasma excitation frequency of 54.24 MHz by varying the flow rates of SiH₄+H₂ mixture in the reaction chamber. It has been found that with increase in gas flow rate from 100 to 300 sccm the defect density, microstructural defect fraction and the crystalline volume fraction in the film decrease. Films deposited at optimum total gas flow rate of 200 sccm with comparable crystalline volume fraction have shown better structural and optoelectronic properties compared to the films deposited at 100 sccm total gas flow rate for application in solar cell. Solar cells have been fabricated using these layers as absorber layers and the maximum cell efficiency obtained is 6.2% (AM1.5, 28 °C) at 200 sccm total gas flow rate. It has been found that material prepared using higher total gas flow rate of 200 sccm together with higher hydrogen dilution is better suited for solar cell application.