Fabrication of see-through thin film photovoltaic solar cells

Abstract

Building-integrated photovoltaic (PV), especially in a semitransparent and/or see-through configuration, has attracted significant attention due to the extended surfaces available for the PV installation including roofs, facades and windows. To this end, the penetration-type PV relying on semitransparent or ultra-thin PV materials, and the aperture-type PV by selectively fabricating see-through holes, have been two major approaches. The ultra-thin film PVs typically suffer from shunt or recombination loss as surface roughness of back and front contacts is frequently comparable to the absorber thickness. On the other hand, in the aperture type semitransparent thin film PV architecture, optical apertures are implemented to independently assign transparent regions on the intrinsic thin film configuration optimized. While laser scribing has been attempted to this end, an unwanted shunt induced by the scribing process has been the main issue especially for the promising thin film PV based on Cu(In,Ga)Se2 (CIGS). In this study, we present our recent achievements in fabricating the aperture type semitransparent CIGS PVs based on a new CIGS architecture with ITO bottom contact. Through optimization of pulsed laser parameters, the measured reduction in PV efficiency was maintained close to the areal fraction of the fabricated aperture within the target range of similar to 15 to 30%. The enabling laser scribing mechanisms in terms of minimized shunt and favorable thin film characteristics will be discussed.