## 3 Results
### Spectroelectrochemistry  
While it would be easy to conclude that this family of dyes behave similarly to the family presented in the work by [PERSON] et al. [50,51], we postulated that there may be another deleterious factor involved in the performance of our devices. The presence of ferrocene as a redox relay was designed to stabilize the TPA via donation of electron density to the TPA upon photoexcitation. As a result, ferrocenium would be generated in the photo-oxidized state. However, in our device fabrication, we use the Z1137 I -/I3 - electrolyte. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Dye** & **VOC (V)** & **JSC (mA/cm2)** & **FF** & **\(\eta\) (\%)** & **N a** \\ \hline
**1a** & 0.65 \(\pm\) 0.004 & 3.97 \(\pm\) 0.570 & 0.58 \(\pm\) 0.026 & 2.71 \(\pm\) 0.345 & 3 \\
**1a**b & 0.69 \(\pm\) 0.002 & 10.4 \(\pm\) 0.1 & 0.76 \(\pm\) 0.50 & 5.5 \(\pm\) 0.1 & - \\
**1b** & 0.33 \(\pm\) 0.044 & 0.22 \(\pm\) 0.118 & 0.21 \(\pm\) 0.117 & 0.028 \(\pm\) 0.004 & 3 \\
**1c**b & 0.57 \(\pm\) 0.003 & 2.40 \(\pm\) 0.1 & 0.53 \(\pm\) 0.0008 & 0.70 \(\pm\) 0.1 & - \\ \hline
**2a** & 0.70 \(\pm\) 0.013 & 4.10 \(\pm\) 0.097 & 0.71 \(\pm\) 0.077 & 3.70 \(\pm\) 0.483 & 6 \\
**2b** & 0.49 \(\pm\) 0.141 & 0.70 \(\pm\) 0.254 & 0.49 \(\pm\) 0.154 & 0.30 \(\pm\) 0.096 & 7 \\
**2c** & 0.26 \(\pm\) 0.028 & 0.17 \(\pm\) 0.025 & 0.21 \(\pm\) 0.026 & 0.018 \(\pm\) 0.002 & 6 \\
**2d** & 0.49 \(\pm\) 0.014 & 0.69 \(\pm\) 0.087 & 0.70 \(\pm\) 0.307 & 0.43 \(\pm\) 0.008 & 6 \\
**2e** & 0.30 \(\pm\) 0.033 & 0.11 \(\pm\) 0.037 & 0.37 \(\pm\) 0.150 & 0.022 \(\pm\) 0.004 & 6 \\ \hline \hline \end{tabular}  
* electrolyte combination used was Z1137. See supporting information for device fabrication details. **b** Additional entries for **1a** and **1c** were previously reported by [PERSON] et al. [50,51].  
\end{table} 
Table 2: Photovoltaic performance of DSSCs based on the ferrocene-based dyes compared to benchmarks **2a** bichromic-bipodal dyes. Iodides are both coordinating and nucleophilic, so we hypothesized that another possible pathway to poor device performance could be dye reactivity with the electrolyte with either the ambient or photo-oxidized conditions. In previous work, combining ferrocenium and tri-iodide redox couples showed no deleterious effects [58]; however, owing to the complex nature of the electrolyte additives and because no attempt was made to strictly remove oxygen from the electrolyte or fabrication process, the potential for ferrocenium to react [2; 58; 59] was seen as a realistic possibility. To examine this further, we performed spectroelectrochemistry experiments (Figure 4) on aldehyde **3c** in acetonitrile and separately in the electrolyte mixture. While there was some pseudo-reversibility observed in **3c** at higher oxidation potentials (>1.3 V vs. NHE, Figure 3a), this dye precursor had the most promising optical properties (similar to **3a**--Figure 2a), so we elected to study this system spectroelectrochemically in acetonitrile (Figure 4a). Acetonitrile was chosen to parallel the \(\mathrm{I}^{-}/\mathrm{I}_{3}\)\({}^{-}\) electrolyte solvent used in the fabrication of our DSSC devices. Figure 4a shows the gradual increase in the absorption of the ferrocenium cation over time at the oxidation potential of 0.9 V vs. NHE. This was an expected observation based on the electrochemistry previously discussed. The <400 nm region of the spectra has rich spectroelectrochemistry as well, but the behavior here is not particularly relevant for the argument herein. In Figure 4b, a similar experiment is shown, but in addition to **3c**, a roughly 10-fold amount of \(\mathrm{I}^{-}/\mathrm{I}_{3}\)\({}^{-}\) electrolyte  
Figure 4: Spectroelectrochemistry of **3c** in acetonitrile (MeCN, 7.0 \(\times\) 10\({}^{-4}\) mol/L) using an optically transparent thin layer electrochemical (OTTLE) cell.