This option opens
new applications for TFSCs where it can be directly coupled to the
electrochemical energy storage, e.g. H2 production by means of water
splitting [2,3]. One other direct way of coupling the solar cell to energy
storage is to connect it to a rechargeable battery. High voltages reached
by multijunction TFSC are of interest here as well. For application in
integrated photovoltaic PV/battery set-ups, multijunction solar cells
delivering voltage of up to 3 V can be used directly to charge storage
batteries [4]. For practical purposes, it is important that these multijunction
solar cells are able to charge storage batteries at illumination
conditions different from the standard AM1.5 under which the cells are