Effects of nickel thickness on metal-induced growth of silicon films for heterojunction solar cells

Microcrystalline silicon (mc-Si) thin films were epitaxially grown by the metal-induced growth process. The effects on the resulting grains of mc-Si were examined with respect to variation in nickel catalyst thickness. Results show that there is a minimum thickness (75 Å) below which the deposited silicon film did not properly form microcrystalline grains. However, as the thickness was increased beyond this level, the grain size and uniformity increased with grains of 1–1.5 μm diameter for 170-Å-Ni and 2 μm diameter for 300 Å Ni. The current-voltage characteristics of Au Schottky photodiodes revealed potential as a solar cell device, having shortcircuit current density, Jsc, of 2.53 mA/cm² and open-circuit voltage, Voc, of 0.19 V. The possibility of fabricating heterojunction solar cells was also investigated by studying a hydrogenated amorphous silicon and nanocrystalline silicon (a-Si:H / nc-Si) tandem layer deposited by electron cyclotron resonance chemical vapor deposition (ECR-CVD). The current-voltage and spectral response measurement demonstrated their viability as an emitter layer of a solar cell when deposited on a c-Si substrate. The Jsc and Voc were 0.764 mA/cm² and 0.33 V, respectively.