Amorphous and Nanocrystalline Silicon Based Photovoltaic Generation of
Electricity and Hydrogen
Xuming Deng
University of Toledo
Abstract
The presentation will cover two aspects: 1) an overview of hydrogenated
amorphous silicon (a-Si:H) related research activities at UT in
photovoltaic (PV) generation of electricity and photo-electrochemical
(PEC) generation of hydrogen; and 2) the use of hydrogenated
nanocrystalline silicon (nc-Si:H) p-type material to obtain high
conversion efficiency for a-Si:H based solar cells.
The overview on PV and PEC will address the significance for
research in these areas, the relationship of these works to the national
programs, some of the recent accomplishments of UT a-Si PV/PEC group,
and the major issues in these two areas.
A two-phase material with p-type Si nanocrystals embedded in an
a-Si:H matrix is used as the p-layers in triple-junction amorphous
silicon based solar cells to obtain high conversion efficiency. With the
crystal sizes carefully controlled during film growth, the bandgap (Eg)
of these nanocrystals are increased from Eg of crystalline Si (1.1eV) to
Eg of amorphous silicon (~1.7eV), due to quantum confinement. Such a
nc-Si:H p-type material is ideal for PV application due to a number of
unique properties and is used in a-Si solar cells to produce record-high
open circuit voltage.