Low degradation and fast annealing effects of amorphous silicon multilayerprocessed through alternate hydrogen dilution

Alternately hydrogen diluted a-Si:H multilayers are shown to be a promising concept for the fabrication of stable a-Si:H solar cells or other a-Si:H b ased devices. The alternately hydrogen diluted amorphous silicon multilayer s were obtained by toggling both the H-2/SiH4 dilution ratio and the total flow rate of the gases under continuous UV light irradiation into the react ion chamber of a photochemical vapor deposition system. The films were char acterized by Fourier transformed infrared spectroscopy, spectroscopic ellip sometry, cross-sectional transmission electron microscopy, and atomic force microscopy. We applied these multilayers as the active layer of p-i-n type thin film solar cells. The multilayer solar cells are compared to solar ce lls incorporating a-Si:H made from pure SiH4 gas and to solar cells incorpo rating a-Si:H made at a constant hydrogen dilution ratio containing nearly the same hydrogen amount as the multilayer. We report on the light-soaking and annealing behavior of the solar cells. The multilayer solar cell has an exceptionally high recovery rate at low temperatures, which makes the sola r cell degradation behavior highly sensitive to the cell temperature during degradation. Following the relation, D(H)proportional to 1/tau, where D-H and tau are the diffusion coefficient for hydrogen and time constant for an nealing, respectively, the layered structure in the multilayer possibly ele vates D-H, which accounts for rapid stabilization and annealing. (C) 2000 A merican Institute of Physics. [S0021-8979(00)00821-5].