Abstract:
Grain size of polycrystalline semiconductor thin films in solar cells is optimized to enhance
the efficiency of solar cells. This paper reports results on an investigation carried out on
electrodeposited n-type cuprous oxide (Cu2O) thin films on Ti substrates with small
crystallites and sulfidation of them to produce a thin-film solar cell. During electrodeposition
of Cu2O films, pH of an aqueous acetate bath was optimized to obtain films of grain size of
about 100 nm, that were then used as templates to grow thicker n-type nanocrystalline Cu2O
films. XRD and SEM analysis revealed that the films were of single phase and the substrates
were well covered by the films. A junction of Cu2O/CuxS was formed by partially sulfiding
the Cu2O films using an aqueous sodium sulfide solution. It was observed that the photovoltaic
properties of nano Cu2O/CuxS heterojunction structures are better than micro Cu2O/CuxS
heterojunction solar cells. Resulting Ti/nano Cu2O/CuxS/Au solar cell structure produced an
energy conversion efficiency of 0.54%, Voc = 610 mV and Jsc = 3.4 mA cm−2
, under AM 1.5
illumination. This is a significant improvement compared to the use of microcrystalline thin
film Cu2O in the solar cell structure where the efficiency of the cell was limited to 0.11%. This
improvement is attributed mainly to the increased film surface area associated with
nanocrystalline Cu2O films.
