Efficiency improvement of flexible a-SiGe:H solar cells decorated by SiNx composite nanostructures

We report on the experimental demonstration of the efficiency improvement of flexible a-SiGe:H solar cells decorated by SiNx composite nanostructures. The structures, which are composed of SiNx nanodome structures and a thin SiNx film that is underneath the nanodome structures, were implemented via sequential processes using inductance-coupled plasma chemical vapor deposition (ICP-CVD), nanosphere lithography (NSL), and reactive ion etching (RIE). Compared with the a-SiGe:H solar cells without the SiNx composite nanostructures, solar cells with SiNx composite nanostructures exhibit that the surface reflectivity reduces down to less than 5% over the spectrum range of 200-700 nm, and the open circuit voltage (Voc) and fill factor (FF) increase up to 0.76 V from 0.70 V and 52.4% from 38.4% respectively, although the short circuit current density (Jsc) reduces down to 11.6 mA/cm2 from 14.7 mA/cm2. The improvement for Voc and FF indicates that a-SiGe:H solar cells were well passivated by using such SiNx composite structures, which results in the overall enhancement of the conversion efficiency from 4.38% to 5.13% finally. If the absorption of the dielectric composite nanostructures decreases, the higher conversion efficiency should be promisingly achieved in these Si-based thin film solar cells decorated by dielectric composite nanostructures.