Single step method to deposit Si quantum dot films using H2 + SiH4 VHF discharges and electron mobility in a Si quantum dot solar cell

To fabricate quantum dot solar cells of a high efficiency at a low cost, here we propose a Si quantum dot film which is composed of Si nano-crystallites embedded into a-Si:H and a single step method to deposit such Si quantum dot films using H2 + SiH4 VHF discharges. For the method, Si nano-crystallites of a small size dispersion and radicals produced in the discharges are co-deposited on a substrate to form Si quantum dot films. Using the method, we realized a volume fraction of dots in films of 0.3–70%. Photo- and dark-conductivity of films are in a range of 10− 11–10− 9 and 10− 5–10− 4 S/cm, respectively. We have examined effects of the size dispersion of nano-crystallites on electron mobility in a quantum dot Si solar cell by a simulation. The electron mobility in films for a size dispersion of 0.37 nm is about 50% of that in films for no size dispersion.