engleski

Grain boundary defects in RTCVD polycrystalline silicon for solar cells

The electrical and optical properties of polycrystalline silicon films are dominated by grain-boundary defects. Of particular interest is therefore, to obtain a columnar grain growth during the deposition process. In this work we studied properties of RTCVD deposited polycrystalline silicon films suitable for solar cells production. The effect of substrate temperature on texture and paramagnetically active defects of polycrystalline Si-film deposited on mono-Si substrate is studied in the temperature range 870&#61616; C - 1240&#61616; C. Preferential grain orientation is found for all polycrystalline films in the whole range of depositing temperature, with the <110> as the main texture component. Volume fraction of this texture component reaches maximum for 1030 - 1100&#61616; C, while weak <311> and <111> components clearly display slight enhancement for 960&#61616; C. For depositing temperature above 1100 - 1240&#61616; C the density of main <110>-texture component diminishes in favour of isotropic grain orientations. The concentration of paramagnetically active dangling bonds fits nicely with the volume fraction of <110> oriented grains. It is shown that the spreading in growth direction causes formation of highly defective grain boundary regions that are the main source of dangling bonds.

silicon; defects; solar cells; RTCVD; grain boundaries

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