INVESTIGADORES
VAZQUEZ marcela Vivian
congresos y reuniones científicas
Título:
2. Thin Films of CuInSe2 Electrodeposited Using Constant and Pulsed Potentials
Autor/es:
M. H. VALDÉS; M. VAZQUEZ
Lugar:
Praga
Reunión:
Encuentro; 63st Meeting of the Internacional Society of Electrochemistry (ISE); 2012
Institución organizadora:
Internacional Society of Electrochemistry (ISE)
Resumen:
The deposition of thin films of copper indium chalcogenides attracts permanent interest due to their current application in the field of photovoltaic solar cells. These materials show a high absorption coefficient and a band gap energy that matches that of the solar radiation. Many techniques can be used to prepare CuInSe2 supported on various substrates. Among them, electrodeposition presents many advantages: it is cost-effective (mainly because it does not require high vacuum o high temperatures), it may copy intricate geometries and it can be scaled-up into industrial production. In this work, CuInSe2 thin films were electrodeposited on conductive glass using potentiostatic (PoED) and pulsed electrodeposition (PuED). One pulse consisted of a single step between two potential values: E1= between -0.7 and -0.9 VSCE and E2= -0.1 VSCE. Each potential was applied during 10 s and the total number of applied pulses was varied between 20 to 180. In the case of PoED, the chosen potential was applied during 400 to 3600 s. The films were annealed in argon to improve the cristallinity and then etched in a KCN solution to remove undesired CuxSe compounds. The materials were characterized employing grazing incident X-ray diffraction, Raman spectroscopy, scanning electron microscopy and energy dispersive scanning spectroscopy. The films are crystalline and the overall quality improves by annealing in Ar. When compared to films prepared at fixed potentials, the presence of secondary phases seemed to be reduced by using pulsed electrodeposition. X-ray diffraction showed no significant differences between films prepared by PuED and PoED. Instead, micro-Raman spectroscopy revealed that by pulsing the potential the composition and homogeneity improved, so that etching in KCN showed no further benefit. Overall, there seems to be no noticeable quality differences between the films prepared by pulsing the potential at -0.7 or 0.9 V. Instead the thickness increased and the crystallinity of the films improved when more pulses were applied. For both types of electrodeposition, longer times favored the formation of nearly stoichiometric CuInSe2. The formation of CuInSe2 involves the reaction of indium ions with CuXSe compounds, as shown by micro-mapping Raman spectroscopy. Photoelectrochemical tests and I-V curves confirm p-type conduction. The differences observed in composition, morphology and optoelectronic properties of the films were attributed to the current profile imposed on the electrode by each type of electrodeposition.