LAUSR

Cu(I)/(II)-complexes redox couples in dye-sensitized solar cell are of particular interest because of their low reorganization energy between Cu(I) and Cu(II) that minimizes potential loss during sensitizer regeneration thus allows the open circuit voltage of the device over 1.0 V. However, Cu(I)/(II)-based redox couples are reported to coordinate with 4-tert-butylpyridine (TBP), which is a standard additive in the electrolyte and this is believed to account for the poor durability of a Cu(I)/(II)-based DSSC. Despite of TBP-coordination on Cu(I)/(II)-complexes are confirmed in literature, its detailed mechanism has yet to be directly proven. In addition, how TBP coordination with Cu(I)/(II)-complexes affects the stability of the device is never reported. Here, we choose bis(2,9-dimethyl-1,10-phenanthroline) copper(I)/(II) ([Cu(dmp)22+/+]) as the modeling redox couple to investigate its interaction with TBP. It is found [Cu(dmp)2+] is resistive to TBP coordination but [Cu(dmp)22+] could form three new TBP-coordinated compounds. Moreover, it is also confirmed their electrochemical activity on Pt catalyst and mass transfer capability are both demoted significantly. As a result, serious fill factor loss is observed on the stability trail while short circuit current density and open circuit voltage are relatively unaffected. This unique degradation pattern may resemble a feature of Cu(I)/(II)-based redox couple after TBP poison.