A single atom change “switches-on” the solar-to-energy conversion efficiency of Zn-porphyrin based dye sensitized solar cells to 10.5%

Abstract

<div> In this work we report how crucial is the correct design of the porphyrin sensitizers in Dye Sensitized Solar</div> <div> Cells (DSSCs). Only a single atom change switches-on the efficiency from 2&ndash;3% to over 10% under</div> <div> standard measurement conditions. We used the 2,1,3-benzothiadazole (BDT) group, as a p-conjugated</div> <div> linker, for the porphyrin LCVC01, a thiophene moiety for the porphyrin LCVC02 and also the furan group</div> <div> for the LCVC03 porphyrin, as molecular spacers between the BDT fragment and the molecule anchoring</div> <div> group, respectively. These three porphyrins were investigated for their application in DSSC devices. All the</div> <div> devices were characterized and found to achieve a record cell efficiency of 10.5% for LCVC02 but only</div> <div> 3.84% and 2.55% for LCVC01 and LCVC03 respectively. On one hand, the introduction of a thiophene,</div> <div> instead of a furan group, illustrates the importance of introducing a chemical group as a spacer, such as</div> <div> thiophene, between the BDT and the anchoring group. On the other hand, the selection of this group has</div> <div> to be correct because the change of a single atom increases the charge recombination rate and decreases</div> <div> the device performance. These changes can be rationalized by analyzing the dye dipoles and their interactions.</div>