Research and development of CuInSe[2]-based photovoltaic solar cells.

The work reported in this thesis includes the growth and characterisation of CuInSe[2]-based materials as well as the assessment and development of CuInSe[2]-based solar cells by the technique of electrodeposition.Cu(InGa)(SeS)[2] layers grown on glass/molybdenum by the two-stage method at Showa Shell have been used for comparison.Electrodeposition of window materials (ZnSe and CdS) on glass/TCO substrates following the conditions prior-established at Sheffield Hallam University has been achieved. CuInSe[2] films have been successfully grown on glass/TCO by electrodeposition. The semi-conducting layers were characterised to investigate their crystallinity, morphology, composition, optical and electrical properties. The structure of the films was characterised by XRD and Raman spectroscopy. The morphology was studied by SEM and AFM. The elemental bulk analysis was performed using XRF and ICPMS. The elemental surface analysis was performed using XPS and the depth profile analysis was studied by GDOES. The optical properties were characterised by optical absorption and the conductivity type was determined by PEC measurements. The conditions of electrodeposition and post deposition treatments were found to influence strongly the properties of the electrodeposited films. Near-stoichiometric films grown by electrodeposition are polycrystalline with a (112) preferential orientation of the chalcopyrite structure. CIS films appear dense with a good mechanical adhesion to the conducting oxide substrates and show crack-free surfaces with spherical grains electrically well connected to each other with a size up to 1 um. Cu, In and Se atoms are not uniformly distributed within the CIS films and In-rich phases, such as CuIn3Se5, cover the surface of the films. Testing of electrical conductivity shows that the films are generally p-type.I-V and C-V measurements were used to characterise the solar cells based on electrodeposited CuInSe[2]. Early stage CuInSe[2]-based solar cells showed encouraging results with efficiencies up to 15.9 % for the best devices. The maximum values of the V[oc], J[sc] and FF observed for the glass/FTO/ZnSe/CuInSe[2]/Au devices were 0.3 V, 105.0 mA/cm[2], and 50 %, respectively.