Microcrystalline silicon solar cells deposited at high rates

Hydrogenated microcrystalline silicon ($\mu c$ -Si:H) thin-film solar cells were prepared at high rates by very high frequency plasma-enhanced chemical vapor deposition under high working pressure. The influence of deposition parameters on the deposition rate $\left(R_D\right)$ and the solar cell performance were comprehensively studied in this paper, as well as the structural, optical, and electrical properties of the resulting solar cells. Reactor-geometry adjustment was done to achieve a stable and homogeneous discharge under high pressure. Optimum solar cells are always found close to the transition from microcrystalline to amorphous growth, with a crystallinity of about 60%. At constant silane concentration, an increase in the discharge power did hardly increase the deposition rate, but did increase the crystallinity of the solar cells. This results in a shift of the $\mu c$ -Si:H∕$a$ -Si:H transition to higher silane concentration, and therefore leads to a higher $R_D$ for the optimum cells. On the other hand, an increase in the total flow rate at constant silane concentration did lead to a higher $R_D$ , but lower crystallinity. With this shift of the $\mu c$ -Si:H∕$a$ -Si:H transition at higher flow rates, the $R_D$ for the optimum cells decreased. A remarkable structure development along the growth axis was found in the solar cells deposited at high rates by a “depth profile” method, but this does not cause a deterioration of the solar cell performance apart from a poorer blue-light response. As a result, a $\mu c$ -Si:H single-junction $p\text{‐}i\text{‐}n$ solar cell with a high efficiency of 9.8% was deposited at a $R_D$ of 1.1 nm∕s.