Influence on cell performance of bulk defect density in microcrystalline silicon grown by VHF PECVD

Silane depletion dependent ion bombardment and material quality of microcrystalline silicon deposited by VHF-PECVD

“…The solar cell efficiency increases from 3.4% to 6.6%. This improvement is attributed to the lower ion bombardment energy, which has been shown to affect the microcrystalline material quality [1,13,14]. This result has been obtained despite the higher deposition rate (6.5 Å/s compared to 2.9 Å/s) which typically tends to worsen the material quality [12].…”

“…A decrease of crystallinity cannot be explained within the frame of equation (1) as higher RF power, increasing the depletion, should favor the growth of material with a higher crystalline fraction. It has been proposed in the past that ion bombardment is an important factor determining the microcrystalline material quality [1,13,14] and that it affects the crystallinity as well [1]. Indeed, if the same data in Figure 2 are displayed as a function of the plasma potential V p ≈ V pp /4 which is proportional to ion energy accelerated through the plasma sheath and bombarding the substrate [15], it can be noted that in the high depletion regime the plasma voltage is significantly lower than in the low depletion regime (see Figure 3).…”

Nanocystalline silicon solar cells

“…In the case of amorphous silicon cells, buffer layers are known to affect the stability of the cells. It has to be noted that the nanocrystalline silicon cell without using any buffer layer showed absolutely no degradation under light soaking and a stable efficiency of 10% has been achieved in that case [37]. This cell has a moderate Voc of 0.52 V, but enjoys a high stabilised efficiency.…”

Limiting factors in the fabrication of microcrystalline silicon solar cells and microcrystalline/amorphous (‘micromorph’) tandems

“…Following previous studies [103][104][105][106][107], a novel microcrystalline process regime for deposition at 10 Å /s, where RF power density is maintained at low values compared to other process regimes [29], was investigated at IMT Neuchaˆtel. It was observed that by increasing the pressure and silane depletion, microcrystalline material quality could be improved [106,108].…”