AbstractsBiology & Animal Science

Among all thin-film (TF) technologies, photovoltaic (PV) cells based on copper indium gallium diselenide (CIGS) absorbers yield the highest efficiency (>22%). Current approaches and future priorities within the CIGS TF PV community are focused on CIGS thickness reduction to further lower material costs and surface passivation concepts to reduce the electronic recombination at interfaces and further enhance the solar cell performance. These approaches involve novel methods to passivate the front and rear surfaces of the CIGS absorber by implementing (i) alkali post-deposition treatments at the front surface and (ii) rear surface field-effect passivation using gallium grading schemes within the CIGS absorber layer. However, above-mentioned surface passivation approaches have been shown less effective when considering ultra-thin (<400nm) absorber layers. Hence, as an attempt to address these challenges, this thesis work is focused on the “Rear surface passivated ultra-thin CIGS solar cell architectures” (i.e. PercIGS), notably by introducing an aluminum oxide passivation layer at the CIGS/Mo-back contact interface. More specifically this thesis work lied at the interface of material and electronic properties with a focus on novel cell technologies and architectures for next generation TF solar cells. A first major achievement resulted in significantly enhanced cell performance (by 4.5% in absolute values) on ultra-thin (<400nm) CIGS absorber layers, i.e. a reduced CIGS absorber usage (by 5-6 times) compared to the conventional CIGS thickness (> 2µm). Additionally, in-depth analyses on the materials and devices were carried out using advanced opto-electrical and material characterization techniques to understand, correlate and optimize these properties towards stable, efficient solar cells. Lastly, to generalize these electronic and interface passivation effects on the CIGS solar cell performance, for the first time, a simulation model has been developed using SCAPS TF PV software. (FSA - Sciences de l'ingénieur)  – UCL, 2016 Advisors/Committee Members: UCL - SST/ICTM/WECM - Wallonia Electronics and Communications Measurements (plate-forme technologique, UCL - Ecole Polytechnique de Louvain, Flandre , Denis, Delamare, Romain, Vermang, Bart, Xiaohui, Tang, Francis, Laurent, Raskin, Jean-Pierre.