INVESTIGATION ON EFFICIENCY OF HETEROJUNCTION SOLAR CELLS BY THICKNESS VARIATION OF P-TYPE A-SIC:H FILMS PREPARED BY ICP-CVD

摘要

Hydrogenated amorphous silicon carbide films(a-SiC:H) were deposited from a mixture of ethylene,silane and hydrogen, with diborene as the doping gas, using the inductively coupled plasma chemical vapordeposition(ICP-CVD) technique. The influence of gas ratio(C_2H_4/(H_2+SiH_4), B_2H_6) was studied at 600W of RFpower, 30mTorr and 250°C. Deposition rate and optical bandgap of the deposited films was investigated bycontrolling gas ratio. As the C_2H_4 percentage increased, the deposition rate of films decreased and optical bandgapincreased up to 3.0eV. Intensity at the range of 2800～3000cm~(-1), which show the C-H stretching mode, was alsomore increased. Concerning on the influence of diborane(B_2H_6) flow rate, Electrical conductivity of p-a-SiC filmsincreased with increase in B_2H_6 flow rate from 10~(-8) to 1.83 X 10~(-6) S/cm. The p-type a-SiC:H/Crystalline Si solarcells with the various thickness range of 9nm～15nm, were fabricated. A 120nm Al doped ZnO(AZO, Al_2O_3 2wt%doping) as TCO(Transparent conducting oxide)was deposited by RF magnetron sputter. When p layer thickness was12nm, Its conversion efficiency is 9.08% with V_(oc) of 0.85V, FF of 0.271, and Jsc of 12.4mA/cm under the airmass(AM) 1.5 illumination from the front side. Quantum efficiency(QE) measurement on these solar cell showsover 90% in the region between 540nm and 780nm.