Abstract:
The quest and need for clean and economical energy sources have increased interest
in the development of solar energy application. In particular, direct conversion of solar
energy to electrical energy and chemical energy using semiconductor photoelectrodes has
attracted attention for many decades. Among the various metal oxide materials for solar
energy application, a promising material is cuprous oxide (Cu20) and is one of the oldest
known semiconductors. It is low cost and non toxic and its component elements are readily
available. It has a direct band gap of about 2 e V and a high optical absorption coefficient.
Nanocrystalline thin films increase the effective surface area of the films as compared with
the microcrystalline thin films. Therefore preparation of nanoparticles of Cu2 0 is of special
importance to improve the solar energy conversion efficiency. In this study, Cu20 films
were deposited electrochemically on Ti substrates. In our investigation, we have developed
a simple electrochemical technique to fabricate the Cu20/CuxS heterojunction and used it to
prepare a thin film photovoltaic solar cell. Electrodeposited Cu20 thin films on Ti substrates
were sulphided by directly applying an aqueous solution of Na2S on to Cu20 films and
annealed at 200 °C for a few minutes. Then the samples were exposed to NH4S gas for a few
seconds. It was observed that the photovoltaic properties and the diode characteristics of
nano/micro/Cu20/CuxS structures were better than that of micro/Cu20/CuxS structures. The
maximum conversion efficiency of the micro/Cu20/CuxS cell was 0.12% (Voc= 240 m V, and
Isc= 0.86 mA/cm
2
) and that of the nano/micro/Cu20/CuxS cell was 0.28% (Voc= 420 m V, and
I,c= 2.1 mA/cm
2
) under AM1.5 illumination.
