High efficiency high rate microcrystalline silicon thin-film solar cells deposited at plasma excitation frequencies larger than 100Â MHz

Microcrystalline silicon thin-film solar cells were fabricated at high absorber layer deposition rates from 1.0 up to 2.5 nm/s. High efficiencies of 9.6% (1.0 nm/s) and 8.6% (2.5 nm/s) were achieved using a very high frequency (VHF) of 140 MHz for the deposition of all silicon layers (p-i-n). Using such a high frequency in the VHF band is unique in the field of thin-film silicon solar cells. The efficiencies obtained especially at very high rates belong to the highest reported efficiencies so far for this technology. This shows that VHF deposition with frequencies larger than 100 MHz is very well suited for a highly productive solar cell fabrication. The VHF power homogeneity problem can be solved by using for example the linear plasma source concept developed at FAP GmbH/TU-Dresden. We show that the efficiency at very high rates of 2.5 nm/s is limited by an increased crack formation in the absorber layer.