High deposition rate processes for the fabrication of microcrystalline silicon thin films

Microcrystalline silicon absorber layers prepared at high deposition rates for thin-film tandem solar cells

“…Adapting the deposition parameters may strongly influence the reactions in the glow discharge. Varying the deposition power or the deposition pressure for example leads to a modification of the ion bombardment of the growing film which in turn influences the growth properties of microcrystalline silicon [12]. The fact that the quantum efficiency of the top solar cell is not strongly affected by the application of the processes leading to high deposition rates for the absorbing layer of the bottom solar cell shows the energies of the bombarding ions are not sufficient to damage the i-n interface of the top solar cell.…”

“…Silicon layers were deposited by plasma enhanced chemical vapor deposition (PECVD) on 10 cm × 10 cm large substrates using a clustertool deposition system which is described in detail in reference [12]. For the a-Si:H top solar cell and the μc-Si:H bottom solar cell the p-i-n deposition sequence was used in the superstrate configuration.…”

“…For the solar cells where the μc-Si:H i-layer was processed at 5 hPa the deposition power was varied between 50 W and 400 W while the SC was varied from 2.4% to 7.0%. The simultaneous variation of the deposition pressure, the deposition power, and the silane concentration was necessary to achieve device grade μc-Si:H i-layers at elevated deposition rates [12] and thus to guarantee the optimal processing conditions for the fabrication of high quality thin-film solar cells. Processes leading to device grade microcrystalline silicon were presented 45201-p2 Table 1.…”

“…The photovoltaic parameters describe the efficiency η, the fill factor FF, the open-circuit voltage Voc, and the short-circuit current density Jsc. in an earlier parameter study [12]. The criteria to classify silicon layers as device grade material have been taken from [2,18].…”

“…In this study we investigated based on the results of our earlier studies [10][11][12] the effect of an increased deposition rate for the μc-Si:H absorber layer on the quality of state of the art thin-film tandem solar cells. Here, we also investigate the effect of high deposition rate used for fabrication of μc-Si:H bottom cell on the stability of the tandem solar cells under light induced degradation.…”