TQT exhibits multifunctional luminescence characteristics, such as polymorphism and mechanochromic, with potential application in OLEDs. An extremely high photoluminescence quantum yield of 96.5% is achieved in CBP: TQT-G doped film.

The development of highly efficient cyclometalated phosphorescent iridium(III) complexes is greatly promoted by their rational molecular design. Manipulating the excited states of iridophosphors could endow them with appealing photophysical properties, which play vital roles in triplet state-related photofunctional applications (e.g., electroluminescence, photodynamic therapy, etc.). In general, the most effective approach for decreasing the emission energies of iridophosphors is to extend the π-skeleton of ligands. However, the π-extension strategy often results in decreased solubility, lower synthetic yield, decreased photoluminescence quantum yield, and so forth. In this work, a simple yet efficient strategy is proposed for the effective excited-state manipulation of 2-phenyllepidine-based iridophosphors. Surprisingly, dramatic tuning of phosphorescence wavelength (∼70 nm) is achieved by simply controlling the position of a single methoxyl substituent on these iridophosphors. An oxygen-responsive iridophosphor featuring far-red emission (660 nm), long emission lifetime (1.60 μs), and high singlet oxygen quantum yield (0.73) is employed to realize accurate oxygen sensing in vitro and in vivo, and it also shows efficient photodynamic therapy in cancer cells, making it a promising candidate for the efficient image-guided photodynamic therapeutic agent. This molecular design strategy clearly demonstrates the advantages of designing novel longwavelength emissive iridophosphors without increasing the π-conjugation of the ligand.

A non-doped device based on TPA1 demonstrates deep-blue emission at 430 nm with a CIEy value of 0.037 and an EQEmax value of 4.36%.

Understanding the structure−property relationships in organic semiconductors is crucial for controlling their photophysical properties and developing new optoelectronic materials. Quadrupolar molecules, donor−acceptor−donor (DAD), have attracted extensive attention in various optoelectronic applications. However, the systematic studies on the differences on photophysical properties between DAD and simple donor−acceptor (DA) chromophores are rarely reported. Herein we present a comparative study on the excited state dynamics of DA and DAD fluorescence systems using theoretical calculation and transient absorption spectroscopy. Results show that DA and DAD molecules exhibit similar excited state dynamics, which are attributed to the distinctive excited-state symmetry breaking (ESSB) phenomenon observed in a DAD system. The strong photoluminescence (PL) and ultrafast charge separation (CS) from an ESSB-induced partial charge transfer (CT) state were clearly detected in different solvent environments. These results not only offer insight into the excited state dynamics of the DAD fluorescence system but also provide some basic guidelines for designing new optoelectronic materials.

No abstract