The influence of the micro-structure on optical properties of nc-Si:H films for solar cells

The intrinsic hydrogenated nano-crystalline silicon (nc-Si:H) films for p-i-n tandem solar cells have been deposited on the corning 7059 glass substrates by plasma enhanced chemical vapor deposition (PECVD) assisted with direct current bias, and were characterized by Raman and ultraviolet-visible (UV-VIS) transmission spectra. By working on varying hydrogen dilution of Silane (ß) and direct current bias (V_DC) separately, the dependence of the optical properties of nc-Si:H films on the micro-structure properties has been discussed. Results have shown: Well fabricated structure of the films result in a small optical band-gap (E_g). However, when amorphous content, namely lattice disorder, increases, E_g is big. Of micro-structure´s parameters, the decrease of crystal volume (X_C), responsible for nano-structure, is the main cause for blue shift of Raman peak position and the decrease in the Raman intensity. And qualitative and quantitative analysis has carried out to get that X_C influenced E_g more severely than crystalline size by varying ß and V_DC. With X_C varied, E_g showed a contrary change trend correspondingly.