Preparation And Properties Of A-Si: H And Si ₃ 4 Silicon-based Quantum Dots Thin Films

Solar energy is a kind of inexhaustible energy. Solar cells, as one of the most direct means, was limited by its low efficiency and high cost. Silicon-based thin film solar cells, which have the advantages of raw materials abundant in nature, low cost, large-scale available etc., and thus become an important research area. In this thesis,the a-Si: H thin films and silicon quantum dots embedded in Si Nx were mainly studied, and focused on the material preparation, properties characterization and the fabrication and characterization of Si-QDs/c-Si heterojunction solar.In this thesis, hydrogenated amorphous silicon(a-Si:H) thin films were deposited by plasma enhanced chemical vapor deposition. The deposition pressure and substrate temperature of the a-Si:H thin film deposition process had been systematically studied. The results showed that the deposition rate, optical band gap and H-bond environment were affected by both deposition pressure and substrate temperature; the optimal deposition pressure and substrate temperature for depositing a-Si:H films are ranged from 110 to 210 Pa and 230℃, respectively。The intrinsic and Sb-doped Si-QDs thin films embedded in Si3N4 matrix were prepared by magnetron sputtering combined with Rapid thermal processing or Microwave annealing. The properties of intrinsic and Sb-doped Si-QDs thin films with different Si concentration are studied, and found that the crystallinity and Si-QDs size increased with the increase of Si concentration. Si-QDs were formed in all silicon rich silicon nitride thin films under different Si concentration by microwave annealing with annealing temperature of 900 ℃ in 3 min. The Si-QDs size was decreased while the crystallinity increased with the increase of annealing time of RTP. The properties of Sb-doped Si-QDs thin films with different Sb concentration are also studied, and found that the crystallinity and the Si-QDs size were increased with the increase of Sb concentration. This could be correlated to the effect of Sb-induced crystallization. Finally,the Si-QDs/c-Si heterojunction solar cells based on Sb-doped Si-QDs thin films were fabricated, the solar cell with the best photoelectric response had the short current density of 0.42 m A/cm2, the open voltage of 439.3mv, the fill factor of 0.25% and the conversion efficiency of 0.456%.