Cyclometallated Iridium Complexes as Sensitizers for Dye‐Sensitized Solar Cells

Iridium(III) 2‐Phenylbenzimidazole Complexes: Synthesis, Structure, Optical Properties, and Applications in Dye‐Sensitized Solar Cells

“…II and Ir III photosensitizers: (a) N3, (b) "black dye" (TBA = tetrabutylammonium cation), (c) the best Ir III dye. [7] In contrast, iridium(III) easily forms bis-or tris-cyclometalated complexes that demonstrate high thermal and chemical stability, long excited-state lifetimes, and emission color tunability by cyclometalated (C N) ligands variations. [6] Unfortunately, only a relatively low device performance (2.2 %) has been achieved by using the best iridium dye to date (Figure 1, c), which seems to be due to weak light absorbance in the range 500-600 nm.…”

“…[6] Unfortunately, only a relatively low device performance (2.2 %) has been achieved by using the best iridium dye to date (Figure 1, c), which seems to be due to weak light absorbance in the range 500-600 nm. [7] Relationships between the ligand structure and luminescent and electrochemical properties of Ir III complexes have been successfully explored by several groups. [8] As a result, emission maxima as well as values of oxidation potentials of Ir III complexes can be finely tuned by varying the HOMO and LUMO energy levels.…”

Synthesis and Characterization of Diethylphosphonate and Carboxylate-appended Iridium Complexes for the Application on Dye-Sensitized Solar Cells

“…However, in aqueous environment, the carboxylate group can be cleaved from the TiO 2 surface, therefore many water stable anchoring groups have been suggested to replace carboxylates. Among these groups phosphonate have been one of the most studied, [53–56] and have been found to present a more stable anchoring under aqueous conditions . Nevertheless, it is important to remark that phosphonate is usually a less efficient electron transferring group than carboxylate, which can affect the efficiency of solar cells.…”

“…In contrast, LLCT may increase separation distance bringing more stability to the π‐π* states, and also to the MLCT transition. In addition, according to the literature, cyclometalated iridium(III) complexes present less accessible MC states compared to ruthenium‐bipyridine based …”

“…Initially, the studies on Ir(III) complexes were mainly focused on applications in other technologically relevant fields such as OLEDs, chemical sensors, luminescent dyes for cell imaging and as water splitting catalysts . However, since 2006 cyclometalated iridium(III) compounds have being studied for sensitizing TiO 2 and assembling DSSC . In these complexes, the calculated ground‐state redox potentials of the Ir(III/V) couple is positive enough to oxidize the I 3− /I − pair.…”