Absorber layers for n+n-p+ μc-Si solar cells grown by electron cyclotron resonance (ECR) CVD

Thin film n⁺n^-p⁺ solar cells of microcrystalline silicon were deposited by a combination of different chemical vapor depositions, i.e. plasma-enhanced CVD (PECVD), rapid thermal chemical vapor deposition (RTCVD) and electron cyclotron resonance CVD (ECRCVD). The preparation of the 1.5-2 μm thick absorber layer has been carried out by ECRCVD, which was optimized before with respect to the crystallinity of the material and the reduction of contaminants. Dark conductivities in the range of 10^-7 Ω^-1 cm^-1 were finally obtained for nominally undoped (n^-) μc-Si films on glass. The deposition of n⁺ and p⁺ doped films was performed by common 13.56 MHz PECVD or in the case of n⁺ films by RTCVD, too. Solar cells of 1 cm² were obtained by mesa etching and lift-off grid metallization. The cells prepared by these techniques achieved an open-circuit voltage of 374 mV and an efficiency of up to 1.6 % without any optical confinement