Research On Novel Wide Bandgap And High Conductivity Window Layers Of Solar Cells

P-type window layer is one of the most important factors which influence the performance of amorphous silicon (a-Si) and microcrystalline silicon (μc-Si) solar cells. In this paper, a-Si window layers doped with B2H6 or B(CH3)3 and μoSi window layers doped with B2H6 were prepared in a series seven-chamber RF-PECVD system. The process parameters and some properties of the window layers were investigated and their working behaviors on solar cells were examined.It was shown that the dark conductivities of the a-SiC:H window layers doped with B2H6 reached 10-7 S/m and bandgap 1.80~1.95eV. Better performance of the single-junction a-Si solar cell covered with the a-SiC:H window layer was observed with the open- circuit voltage 0.835V, short-circuit current density 13.03mA/cm2, fill factor 0.725 and initial conversion efficiency 7.89%.For the μc-SiC:H window layer doped with B2H6, the dark conductivity of 2.24 S/m was achieved. The initial conversion efficiency of μc-Si solar cell with this window layer was 4.8%. The μc-SiC:H solar cells' efficiency degradation in air were less than 15%.The dark conductivities of the a-SiC:H window layers doped with B(CH3)3 were measured in the range of 10-7 -10-6 S/cm and the bandgap 1.94-2.05 eV. Applying this kind of window layer to a single-junction a-Si solar cell, good results such as the open-circuit voltage 0.886V, short-circuit density 14.486 mA/cm2, fill factor 0.667 and initial conversion efficiency 8.67% were gotten.Furthermore, the plasma optical emission spectra (OES) of the ionization of the working gases were analyzed in situ using a PR-650 spectroscope. From the OES information, it was found that B2H6 and B(CH3)3 contributed differently to the formation and properties of the window layers. Some other conclusions which had instructions to the experiments were also obtained.