High efficiency p-i-n solar cells with ⟨i⟩ layer deposited by hot-wire technique

More stable amorphous silicon (a-Si:H) material obtained with the hot-wire technique requires high substrate temperatures (T_sub>300°C) and low gas pressures (p_dep≈10^-2 mbar). The second condition implies that heat transfer between the heater and the substrate is mainly dominated by thermal radiation; therefore, T_sub is strongly affected by the emissivity ε_surf of the growth surface. Here, it is shown experimentally that ε_surf depends on the thickness of the growing a-Si:H layer; a significant variation in ε_surf during the deposition of the first 3000 Å has been observed. With the help of a new heating concept, we integrated an intrinsic layer deposited at constant T_sub=270°C into a p-i-n solar cells with initial efficiency of 8.7%