## 1 Introduction  
In the development of novel technologies, one of the objectives of materials science is to replace expensive chemistry components with low-cost chemical building blocks [1, 2]. This has been particularly true in the development of the dyestuffs used in dye-sensitized solar cells (DSSCs) [3, 4, 5, 6, 7, 8]. From the first reported high-efficiency DSSC [9], there have been active pursuits to replace ruthenium with less costly metals, or to develop dyes that are entirely metal-free [10]. In this pursuit, Zn-porphyrin DSSC dyes have exhibited some of the highest DSSC performances [11, 12], but other first row metal-based hybrid (organic/inorganic) dyes remain unexplored. While perovskite-based solar cells now dominate next-generation PV literature [13] owing to their superior performance, the DSSC remains a unique manifold to examine the optoelectronic properties of organic molecules and screen their potential applications in integrated devices [14]. Owing to their low cost, redox activity, and position in the periodic table (above ruthenium), iron-containing DSSCs are particularly attractive, but have been considerably less efficient in DSSC applications [15]. [PERSON] et al. [16] reported an iron-containing bipyridyl complex analogous to N3 and observed charge injection into the titania (TiO\({}_{2}\)) semiconductor upon photo-excitation. However, other works using time-resolved electronic absorption spectroscopy studies [17; 18] have shown that these iron complexes have extremely short metal-to-ligand charge-transfer (MLCT) lifetimes and rapid internal conversions competing with charge injection, ultimately lowering their photovoltaic efficiencies. However, a renaissance of iron complexes is being observed thanks in part to the development of N-heterocyclic carbene-Fe based DSSC dyes [19; 20; 21; 22; 23]. Moving away from iron-based complexes as sensitizers, ferrocene-containing hybrid organic dyes have also received considerable attention [24]. Ferrocene (Fc) has been incorporated into organic photovoltaic materials in several ways, including as a donor (D) or acceptor (A) in bulk heterojunction solar cells [25; 26; 27], as a redox mediator and hole transport material in DSSCs [28; 29; 30; 31], and as a dye substituent in a myriad of DSSC dye architectures [32; 33; 34; 35; 36; 37; 38; 39; 40; 41; 42]. In each of these cases, the electron-rich and redox-active behavior of ferrocene is the motivation for its use. However, despite the ubiquitous nature of ferrocene as a redox-active donor, since the report of L1 (Figure 1; **1a**), or 'Sun's dye' in 2007 [43], triphenylamine (TPA) donors have not been successfully conjugated with ferrocene to make DSSC dye candidates [44; 45; 46; 47]. Considering the extensive use of both ferrocene and triphenylamine as donors in the development of DSSC dyes, there are remarkably few reports that see ferrocene attached to TPA as a tandem donor system [48; 49; 50; 51]. Herein, we report a new TPA-Fc dye architecture and examine its potential for optoelectronic applications using DSSC motifs. Our group has previously reported a variety of D-\(\pi\)-A DSSC dye motifs including those containing Fc [39] and TPA [52] donors, and most recently we reported a family of bipodal bis-triphenylamine dyes [53; 54] with the form D-\(\pi\)-D-A (Figure 1; **2a**) that are our most efficient dyes yet. As such, we were intrigued by the work of [PERSON] et al. [50; 51], who modified Sun's dye with ferrocene (Figure 1; **1c**), the only other example of Fc-TPA dyes. In their work they observed that the performance of the Fc-modified dyes was poorer than ferrocene-free dyes in DSSC applications, owing to a faster recombination process (using IR transient absorption studies). They concluded that the twisted intramolecular charge-transfer (TICT), a key feature benefitting TPA dye performance, was disrupted by the intramolecular electron transfer from ferrocene, leading to the deleterious enhanced electron recombination processes.