Silicon thin-film solar cells at high growth rate under constant power-to-flow ratio plasma conditions

• a-Si was prepared at high growth rate using only a RF-PECVD and pure silane.
• Growth rate was increased keeping constant the ratio silane flow to applied power.
• a-Si showed excellent properties in a wide range of deposition conditions.
• Solar cells presented fill factor and efficiency as good as the reference device.
• Variable illumination measurements confirmed a high carrier collection capability.

This work approaches the problem of increasing the growth rate of device quality a-Si:H by using the simplest case, a standard RF-PECVD system and pure silane as feedstock gas. Starting from plasma conditions which provided a high-quality material at very low deposition rates, the silane flow and the applied power (RFP) were proportionally increased. As a result, the growth rate showed an almost linear increase with the RFP. An exhaustive analysis of the material obtained revealed the existence of a wide window in which the structural/optoelectronic properties remain unchanged. Within this window, a-Si:H p-i-n solar cells were fabricated in order to verify the applicability of the procedure proposed to the development of device structures. The initial results showed an excellent behaviour of the solar cells at higher growth rates, without any relevant detriment in the collection capability and fill factor. Thus, the constant power-to-flow ratio is presented as an easy and reliable method to reduce the deposition time which, additionally, could be applied to any variant of plasma CVD system.