Electrical properties of polycrystalline solar cell silicon.

摘要

The electrical properties of polycrystalline silicon (p-type) were investigated by resistivity, C-V, and DLTS measurements. In particular, the influence of oxygen, carbon, and the fast diffusing transition elements (Cu, Ni, Fe, and Cr) in polycrystalline silicon has been studied. Ohmic contacts on polycrystalline silicon specimens were made successfully by Ga-In application by scrubbing or Al evaporation followed by short annealing. For Schottky diodes, Ti/poly-Si (p-type) was used for C-V and DLTS measurements. The objective was to identify the defects which are mainly responsible for the observed electrical changes.;The specimens were Cast and Ribbon polycrystalline silicon with different impurity concentrations. Both specimens were annealed over a wide range of temperatures, between 300;For an investigation of the influence of particular transition elements, the metals (Cu, Ni, Fe and Cr) were intentionally deposited on polished surfaces of the Cast and Ribbon Si specimens, and the electrical properties of specimens doped with transition elements and of undoped specimens were investigated and compared. The electrical properties of various transition metals in polycrystalline silicon showed different behavior depending on the diffusing temperature and cooling rate. The specimens which were intentionally diffused with Cu or Ni did not show any significant electrical change compared with undoped specimens. However, the specimens which were intentionally diffused with Fe or Cr showed a significant decrease of the carrier concentrations and an increase of the resistivities and trap concentrations compared with undoped specimens. The electrical changes are more prominent with the specimens that were quenched or exposed to a higher diffusion temperature.