This thesis focusses on the design of new ruthenium(II) complexes featuring tridentate ligand platforms based on 1,2,3-triazoles. The latter not only offers a facile and modular ligand synthesis but also various coordination modes, thereby enabling the design of functionalized bis(tridentate) ruthenium(II) complexes with tailored properties. It is demonstrated that the notoriously short lifetimes of the charge-separated excited state of bis(tridentate) ruthenium(II) polypyridyl complexes can be substantially prolonged by partially replacing pyridines with 1,2,3-triazolylidenes. Moreover, aiming at application in the dye-sensitized solar cell, different types of bis(tridentate) ruthenium(II) complexes bearing an anionic 1,2,3-triazole-derived ligand as thiocyanate surrogate and a terpyridine-based anchoring ligand were studied. The metal is either coordinated by an N^C^N-cyclometalating ligand featuring peripheral 1,2,3-triazole donors or by a tridentate ligand consisting of two anionic 1,2,3-triazolates and a central pyridine ring. In both cases, the ruthenium(II) complexes exhibit sufficiently long excited-state lifetimes and suitable ground- and excited-state redox potentials for applications in a conventional dye-sensitized solar cell. Accordingly, the new dyes achieved power conversion efficiencies approaching the values obtained with a thiocyanate-containing ruthenium(II) benchmark sensitizer (N749) under identical conditions. Furthermore, it is demonstrated that conductive, photo-redox active metallopolymer films can be obtained via anodic electrolpolymerization of thiophene-functionalized, 1,2,3-triazole-containing cyclometalated ruthenium(II) complexes. Keywords: click chemistry, cyclometalation, dye-sensitized solar cells, electropolymerization, excited-state lifetimes, mesoionic carbenes, photosensitizers, ruthenium(II) complexes, 2,2′:6′,2′′-terpyridine, 1,2,3-triazoles, 1,2,3-triazolylidenes, tridentate ligands. Cyclometallierung, Dreizähnige Liganden, Elektropolymerisation, Farbstoffsolarzellen, Klick-Chemie, Lebensdauer angeregter Zustände, Mesoionische Carbene, Photosensibilisatoren, Ruthenium(II)-Komplexe, 2,2′:6′,2′′-Terpyridin, 1,2,3-Triazole, 1,2,3-Triazolylidene