Abstract:
The solar energy conversion methods using non-conventional semiconductor
materials were studied. Four systems were investigated in
the frame work of this project; solid state photovoltaic system, photoelectrochemical
system, photocatalytic system and dye sensitized solar
cells. An attempt was also made to investigate the photoeffects at
semiconductor interfaces, semiconductor-liquid junctions, and dye
sensitized semiconductor interfaces by measuring various semiconducting
and photophysical parameters.
The methods of preparation of p- and n-type film of p-CuCNS
and their solid state properties were studied. p-Cu S/n-p-CuCNS junction
solar cell was fabricated and the characteristics were determined.
Polycrystalline p-Cu S/n-CdS junction photocathode (where CdS
film deposited on Cu S coated copper substrate) showed a photocurrent
X
quantum efficiency which was several orders of magnitude higher than
that of Cu^S photocathode. The mechanism involved was studied.
Dye sensitized solid state and photoelectrochemical cells were
prepared using p-CuCNS. Enhanced photocurrent quantum efficiency of
a he terojunction CuS/CuCNS photocathode where CuCNS was sensitized
with Rhodamine B was attributed to the presence of a strong space charge
electric field that assist charge separation. A thin layer of dye
sandwiched between p-CuCNS deposited on copper substrate and n-SnO^
coated transparent glass was found to yield photocurrent resulting
frcm light absorption in the dye. Furthermore stabilization and quantum
efficiency were improved by varying surface properties of the devices.
Photocatalyt ic type cells, which can be used for photocleavage
of water and produce energy rich compounds were studied. Silver
phosphate and hydrous cuprous oxide were found to photocatalyse decomposition
of water into oxygen and hydrogen. Again it was found that an
aqueous suspension of hydrous cyprous oxide photoreduce carbonic acid
selectivity to methanol with selfsacrification. The high yield and
selectivity was attributed to strong chemisorption of CQ, ; highly
negative flat band potential and multi-electron transfer.
