CuInSe 2 films prepared by three step pulsed electrodeposition. Deposition mechanisms, optical and photoelectrochemical studies

p-Type semiconducting copper indium diselenide thin films have been prepared onto In 2O 3:Sn substrates by a recently developed pulse electrodeposition method that consists in repeated cycles of three potential application steps. The Cu-In-Se electrochemical system and the related single component electrolytes were studied by cyclic voltammetry to identify the electrode processes and study the deposition processes. In situ atomic force microscopy measurements during the first 100 deposition cycles denote a continuous nucleation and growth mechanism. Particles removed by film sonication from some of the films were characterized by transmission electron microscopy and determined to consist in nanoscopic and crystalline CuInSe 2. The remaining film is still crystalline CuInSe 2, as assessed by X-ray diffraction. The chemical characterization by combined X-ray photoelectron spectroscopy, X-ray fluorescence and inductively coupled plasma optical emission spectroscopy, showed that films were Cu-poor and Se-poor. Raman characterization of the as-grown films showed that film composition varies with film thickness; thinner films are Se-rich, while thicker ones have an increased Cu-Se content. Different optical absorption bands were identified by the analysis of the UV-NIR transmittance spectra that were related with the presence of CuInSe 2, ordered vacancy compounds, Se, Cu 2-xSe and In 2Se 3. The photoelectrochemical activity confirmed the p-type character and showed a better response for the films prepared with the pulse method. © 2011 Elsevier Ltd. All rights reserved

Study and improvement of aluminium doped ZnO thin films: Limits and advantages. Electrochimica Acta 109 (2013) 117-124

ZnO: Al films were deposited at 70◦C at a fixed −1.1 V potentialonto ITO substrates from a 0.01 MZn(NO3)2+ x Al(NO3)3•9H2O electrochemical bath, with Al3+concentrations between 0 and 2 mM. Elec-trodeposition conditions were optimized to remove bubbles, increase grain size homogeneity and ensure adherence. Films were characterized by field emission scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, UV–vis transmittance, electrochemical impedance spectroscopy and photocurrent spectroscopy. Films were crystalline with the wurtzite structure and present a morphology made of hexagonal nano-pillars. It was found that Al incorporation increases gradually up to ∼11 at% forsamples prepared within the concentration range 0.0–0.3 mM Al3+in the bath. For higher Al3+contents(>0.4 mM) an amorphous Al2O3-like compound develops on top of the films. In the grown films with Alcontents up to 11 at%, changes in the optical band gap from 2.88 eV to 3.45 eV and in the carrier densi-ties from 1019to 1020cm−3were observed. The blue shift in the band gap energy was attributed to the Burstein-Moss effect. Changes in the photocurrent response and the electronic disorder were also dis-cussed in the light of Al doping. Optical transmittances up to 60% at 550 nm were obtained, thus making these films suitable as transparent and conductive oxide films