Novel application of MgF2 as a back reflector in a-SiOx:H thin-film solar cells

We present high-quality a-SiOx:H solar cells with a very thin i-layer of 100 nm fabricated at a low temperature of 100 degrees C. To boost the photocurrent with such a thin absorber, we suggested the application of a low-index MgF2 buffer at the n-type nanocrystalline silicon oxide (n-nc-SiOx:H)/Ag nanotextured interface to suppress the absorption loss at the Ag back contact. The introduction of MgF2 of only a few nanometers (similar to 4 nm) thickness enhanced the reflection at the n-nc-SiOx:H/Ag interface, which resulted in the reinforcement of the short-circuit current by about 7.3% from 9.60 to 10.30 mA/cm(2) while almost maintaining V-oc and FF. We demonstrated the efficiency improvement of up to 7.66% by MgF2 at the back contact. (C) 2014 The Japan Society of Applied Physics