M.E Calixto

Compositional and optoelectronic properties of CIS and CIGS thin films formed by electrodeposition

Abstract CuInSe2 (CIS) and Cu(In,Ga)Se2 (CIGS) thin films were prepared by electrodeposition and processing. The influence of film deposition parameters such as bath composition, pH, deposition potential and material purity on film properties was studied. The structural, morphological, compositional and opto-electronic properties of electrodeposited and selenized CIS and CIGS thin films were characterized using various techniques. As-deposited as well as selenized films exhibited a compact or a granular morphology depending on the composition. The film stoichiometry was improved after selenization at 550°C in a tubular furnace. The films are formed with a mixed phase composition of CuInSe2 and CuIn2Se3.5 ternary phases.

CIS and CIGS based photovoltaic structures developed from electrodeposited precursors

Abstract In the present study we report the electrodeposition and characterization of CIS and CIGS thin films and a post-deposition thermal processing in vacuum to improve the film stoichiometry by incorporating additional In, Ga and Se. Different kinds of analyses showed that CIS as well as CIGS possess a very thin In-rich surface n-layer. The formation and characterization of solar cell structures from the electrodeposited precursor with the configuration glass/Cr/Mo/CIS(CIGS)/CdS/ZnO/MgF 2 is also reported. The optoelectronic properties such as Voc, Isc, FF, η etc. of the cells are presented.

Fundamental studies on large area Cu(In,Ga)Se2 films for high efficiency solar cells

This work reports the growth and characterization of thin films of Cu(In,Ga)Se2 (CIGS), which were grown by sequential sputtering, electrodeposition, and physical vapor deposition. Photovoltaic cells have been fabricated using these films with CdS heterojunction partners and the performance has been characterized. The effect of annealing conditions (temperature and duration) on the CIGS film microstructure and corresponding device performance has been investigated. Structure-property correlations were made using diffraction studies and Rietveld analysis. SEM studies were carried out to understand the effect of microstructure of the CIGS films on the solar cell efficiency. Cell efficiencies in excess of 10% have been achieved by using optimized annealing conditions. In addition, the optical properties of the sputtered CIGS films were characterized using variable angle spectroscopic ellipsometry and sputtered CIGS films were found to have optimum band gap. r 2001 Elsevier Science B.V. All rights reserved.

Electrodeposited and selenized (CuInSe2) (CIS) thin films for photovoltaic applications

Abstract In the present communication, the authors report results on the characterization of electrodeposited and selenized (CuInSe 2 ) (CIS) thin films. The selenization process was carried out using a technique called chemical vapor transport by gas (CVTG). The precursors as well as selenized films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron microprobe analysis (EPMA). The film stoichiometry improved after selenization at 550°C. The films were formed with a mixed composition of the binary as well as the ternary phases.

Deposition of smooth Cu(In, Ga)Se2 films from binary multilayers

Abstract Thin film photovoltaic devices based on CuInSe2 (CIS) prepared by vacuum deposition have shown efficiencies greater than 17%. However, inexpensive large-area uniform-thickness photovoltaic devices are likely to require non-vacuum deposition techniques. We discuss in this paper electrodeposition of CIS films using multilayers of binary selenides and, post-deposition selenization and thermal annealing. A sequential electrodeposition of Cu/In2Se3/Cu2−xSe on Mo-on-glass substrates was done potentiostatically at varying potentials, pH and deposition time. We have obtained crystalline chalcopyrite CuInSe2 films with phase content greater than 95%. The surface of the films is specularly reflecting. We also present here a study of sputtered CIGS films using multilayers of binary selenides, and one-step electrodeposition of CIS films.

Cu(In, Ga)Se2 based photovoltaic structure by electrodeposition and processing

CuIn 1-x Ga x Se 2 (CIGS) thin films were formed from an electrodeposited CuInSe 2 (CIS) precursor by thermal processing in vacuum in which the film stoichiometry was adjusted by adding In, Ga and Se. The structure, composition, morphology and opto-electronic properties of the as-deposited and selenized CIS precursors were characterized by various techniques. A 9.8% CIGS based thin film solar cell was developed using the electrodeposited and processed film. The cell structure consisted of Mo/CIGS/CdS/ZnO/MgF2. The cell parameters such as J sc , V oc , FF and η were determined from I-V characterization of the cell.

Porous CdS:CdO composite structure formed by screen printing and sintering of CdS in air

Abstract A porous CdS:CdO composite structure was formed by screen printing of CdS powder and sintering in air at high temperature. The X-ray diffraction analysis of CdS sintered at different temperatures revealed that a CdO formation in the CdS matrix is by the phase transformation of CdS, which may be stated as CdS–CdSO4–CdO. The structure, composition and photosensitivity of this composite structure depend on the sintering temperature, sintering atmosphere and the flux to semiconductor (F/S) ratio. The results indicate that the screen printed CdS:CdO structure may be used as a photoconductor in solid state devices and as a photoelectrode in photo-electro-chemical energy conversion systems.

Depth profile analysis of CuInSe2 (CIS) thin films grown by the electrodeposition technique

Abstract In this study, we report the results obtained from the auger electron spectroscopy (AES) depth profiling of CIS thin films grown by the electrodeposition technique. This result enables one to do a comparison between the bulk and superficial elemental compositions. The AES result is also compared with that obtained by the inductively coupled plasma (ICP) spectroscopy. These results support our proposition that the electrodeposited CIS film has a Cu-rich bulk region and an In rich surface, which leads to the formation of an n-layer (CuIn2Se3.5) on the top of the p-type CIS (CuInSe2) phase

Characterization of co-electrodeposited and selenized CIS (CuInSe2) thin films

Abstract The structural, morphological, compositional and photoelectrochemical properties of co-electrodeposited and selenized CIS thin films were characterized using various techniques. As-deposited as well as selenized films exhibited a compact or a granular morphology depending on the composition. The film stoichiometry was improved after selenization at 550 °C in a tubular furnace. The film conductivity type, carrier concentration and flat-band potential were determined from the photoelectrochemical studies. The films are formed with a mixed composition of the binary as well as the ternary phases. From the results of these studies, a model is suggested for the superficial as well as the bulk conductivity types of the film.

Photovoltaic structures based on polymer/semiconductor junctions

CdTe and CuInSe 2 (CIS) thin films were electrodeposited and characterized for photovoltaic applications. Schottky barrier-type photovoltaic junctions were obtained using a heavily doped PMeT (poly-3-methylthiophene), prepared by electropolymerization, displaying nearly metallic behavior, and semiconductors such as CdTe and CIS obtained by electrodeposition. The photovoltaic structures formed and studied are Mo/CIS/PMeT/grid and Mo/CdTe/PMeT/grid Schottky barrier junctions. Solar to electrical conversion eƒciency of the order of 1% was obtained in the case of PMeT/CIS and PMeT/CdTe junctions. ( 1998 Elsevier Science B.V. All rights reserved.