Building more efficient solar cells
Solar cells fabricated from Copper Indium Gallium diSelenide (CIGS) are significantly more efficient at converting incident sunlight into electricity than conventional cells made from amorphous Silicon (a-Si). The problem is that they are considerably more expensive to manufacture. Two Spanish (CIEMAT and INASMET) and two German (IPE and ZSW) organisations specialising in renewable energy research combined their resources and knowledge to address this challenge. Part of their research focused on various treatments of the metals used as a substrate for the CIGS film. The smoother the metal substrate, the better. Different methods, including electrochemical and mechanical polishing as well as SiOx deposition, were tested on two metals: ferritic chromium steel and titanium. The resulting foils were assessed for smoothness using atomic-scale analysis methods like Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and Secondary Ion Mass Spectrometry (SIMS). The results of the analysis indicate that mechanical polishing is preferable. The Spanish and German scientists also evaluated the effectiveness of adding dielectric and conductive layers on top of the foils to block contamination of the CIGS film by the metallic substrate. The outcome of the joint effort is a new chemical treatment that eliminates harmful elements before they accumulate to destructive levels. The consortium is looking to extend this research further in order to ultimately make CIGS technology economically competitive with that of a-Si.
