The influence of temperature on the CIGS films deposited by picosecond laser ablation
for solar cells applications
Cornelia Sima
a
, Ovidiu Toma
b
a
National Institute for Laser, Plasma and Radiation Physics, Laser department, 409
Atomistilor, P.O. Box MG-36, 077125, Bucharest-Magurele, Romania
b
University of Bucharest, Faculty of Physics, 405 Atomistilor, P. O. Box MG-11,
077125, Bucharest-Magurele, Romania
E-mail:
Tel/Fax: +4021 4574027
CIGS films were deposited by picosecond laser ablation method using a Nd:YAG laser (8 ps,
0.2 W, 50 kHz, 532 nm) starting from a CuIn
0.7
Ga
0.3
Se
2
target and optical glass substrate. The
films were deposited in vacuum at 3x10
-5
Torr. Target-substrate distance was 4 cm. The
deposition time was 2 hours. The films were deposited at room temperature (RT) and
different temperatures in the range of 100-400
0
C.
The goal was to study the influence of the deposition temperature on the film characteristics
in order to meet the suitable requirements for solar cells applications regarding crystallinity,
composition, film thickness and optical properties.
In this way, structure, film morphology, composition and optical measurements were made
by X ray diffraction, scanning electron microscopy (energy dispersive X ray spectroscopy)
and spectroscopic ellipsometry.
It was obtained crystalline films starting with 200
0
C deposition temperature with dominant
peak corresponding to CuIn
0.7
Ga
0.3
Se
2
(112); thickness decreased gradually with temperature
increasing, at RT it was about 1.44 µm and decreased to 0.72 µm at 400
0
C ; atomic
composition in the case of In, Ga, Se increased after annealing while in the case of Cu
decreased comparing with RT; optical constants (refractive indices, extinction coefficients,
optical band gaps) of CIGS films were computed. Refractive indices exhibited a short
tendency to decrease by increasing the deposition temperature, while the optical band gaps
values for CuIn
0.7
Ga
0.3
Se
2
laser ablated thin films were around 1.3 eV.
PS1 1
-157-
