In pursuing novel efficient lighting technologies and materials, phosphorescent cyclometallated Ir(iii) complexes have been prominent due to their wide color arrays and highly efficient electroluminescence. Their photophysical properties are strongly influenced by spin-orbit coupling exerted by the iridium core, usually resulting in intense, short-lived emission, which can be systematically tuned as a triumph of molecular engineering. This Perspective aims to present recent breakthroughs and state of the art on emissive Ir(iii) compounds, in particular a personal account on heteroleptic [Ir(N^C)2(L^X)](+) complexes, addressing the mechanistic concepts behind their luminescence. Their fascinating photophysical properties strengthen application in more-efficient light-emitting technologies, such as organic light-emitting diodes and light-emitting electrochemical cells.

All-inorganic layer-by-layer TiO2–Nb2O5 films were applied as underlayers in DSCs, leading to an expressive improvement on the conversion efficiency.

Novel fac-[Re(CO)3(dmcb)(trans-stpyR)]+ complexes, dmcb = 4,4'-dimethoxycarbonyl-2,2'-bipyridine, have been judiciously engineered to absorb at lower energies and sensitize trans-4-styrylpyridine (trans-stpy) or trans-4-(4-cyano)styrylpyridine (trans-stpyCN) photoisomerizable ligands up to 436 nm of irradiation. Moreover, these complexes exhibit remarkable photoreversibility, in particular fac-[Re(CO)3(dmcb)(trans-stpyCN)]+ (Φ255 nmcis→trans = 0.26 ± 0.02). Their distinct and noteworthy photochemical and photophysical behavior are described in this work. The main emphasis of this study is that the complexes efficiently sensitize stilbene-like ligand isomerization toward use in potential solar device applications.

An innovative all-nano-TiO2 thin film capable of enhancing dye-sensitized solar cell (DSC) photoefficiencies was prepared by a layer-by-layer method beneath the meso-TiO2 film, employing acid and basic nano-TiO2 sols as cations and anions, respectively. TiO2 syntheses were performed under absolute control to lead to appropriate morphological and optical properties to yield high-quality compact films using profilometry, tuning, and scanning electron microscopy. A detailed study by photoelectrochemical parameters, incident photon-to-current efficiency, electron lifetime, and electrochemical impedance spectroscopy demonstrates that the physical contact between FTO and the electrolyte is prevented and the role of the compact film has been elucidated. DSCs with TiO2 bilayers on top of FTO improved the conversion efficiency up to 62%, mainly because of the prevention of FTO/I3(-) charge recombination and an improved contact between FTO and TiO2.

In this work, efficient trans ⇌ cis photoswitchings of 4-(4-cyano)styrylpyridine (stpyCN) coordinated to organometallic bipyridyl tricarbonyl rhenium(I) complexes, fac-[Re(CO)(NN)( trans-stpyCN)], where NN = 2,2'-bipyridine (bpy) or 4,4'-dimethyl-2,2'-bipyridine (dmb), are described. For both complexes, the true trans-to- cis quantum yields determined by H NMR spectroscopy are similar at 313, 334, and 365 nm irradiations (Φ ∼ 0.45), with a small decrease at 404 nm (Φ ∼ 0.37). The investigated complexes also exhibit significant quantum yields for the reversible cis-to- trans photoreactions (Φ = 0.22). The luminescent properties of these complexes were also analyzed in different media to elucidate a key role of the IL state in photophysical and photochemical processes, giving new insights on their intriguing photobehavior.