These ligands are able to impose a change in LUMO level which is so called red shift in absorption properties of dye complex in dye sensitized solar cells.
How this is related to better electron transportation from redox electrolyte to dye complex?
Does it happen because of relatively larger electron affinity?
Isothiocyanate is a fairly strong pi acceptor ligand. If your dye is a 4 coordinated complex like that of Cr(II), having a few d electrons, lowering of LUMO relative to the average energy level may happen due to the square planar structure, in which 3 electrons occupy the two lowest energy orbitals derived from t2g set and one eg orbital above those t2g set is vacant. Better electron transport of course may be related to a fairly high electron affinity of NCS- as a pi acceptor.
In general, lowering the LUMO will lower the output voltage of the cell. Since much of the voltage of a DSSC is lost in the hole transfer mechanism I doubt if changing the LUMO will make any improvement and is more likely to make things worse.
- Badges
- Science topic