Fluorine-free blue-emitting cationic iridium complexes with oxadiazole-type cyclometalating ligands and their use in light-emitting electrochemical cells

Elucidating the Nonradiative Deactivation Pathways in a Cationic Iridium Complex with 2,4-di(1H-pyrazol-1-yl)Pyridine as the Ancillary Ligand

“…Detailed photophysical characteristics are summarized in Table 1. Similar to other phosphorescent cationic iridium complexes, 9,15,20,23,24 [Ir(ppy) 2 (bipzpy)]PF 6 exhibits strong absorption bands in the ultraviolet region, which are assigned to spin-allowed ligand-centered 1 π−π* transitions, and relatively weak abortion bands (>350 nm) that extend to the visible region, which are assigned to 1 MLCT (metal-to-ligand charge-transfer), 1 LLCT (ligand-to-ligand charge-transfer), 3 MLCT, 3 LLCT, and ligand-centered 3 π−π* transitions. 8,40−42 The spin-forbidden triplet transitions gain partial allowance owing to the strong spin−orbital coupling of the heavy iridium atom.…”

“…As shown in Table 3, the excitation energies of T 1 , T 2 , and T 3 states are very close (within 0.1 eV) to each other, which indicates that the three triplet states lie close in energy, and in principle, the phosphorescence could occur from any of them. 20,23,44 As revealed by the photophysical characterizations, in the CH 3 CN solution or in the lightly doped PMMA film, the phosphorescence comes mainly from a ligandcentered 3 π−π* state. In these scenarios, the T 1 or T 2 states with notable ppy-centered 3 π−π* character should account for the emitting triplet state.…”

“…He et al found that replacing one pyridine ring in bpy with an electron-rich pyrazole ring, e.g., 2-(1 H -pyrazol-1-yl)­pyridine (pzpy), results in a significant LUMO destabilization, leading to an over 100 nm blue-shift of light emission . Since then, pzpy-type ancillary ligands have been widely adopted to construct blue-emitting cationic iridium complexes. ,,− …”

Recent Progress in Sublimable Cationic Iridium(III) Complexes for Organic Light‐Emitting Diodes

“…Besides, deeper investigation is also imperative referring the underlying sublimation mechanism, for instance, how the cations and anions ultimately separate by heat, travel under vacuum and finally deposit onto the substrates during device preparation. Moreover, sublimable cationic iridium(III) complexes also show great promise in other organic semiconductors, since their solution‐processable analogues have been widely used in light‐emitting electrochemical cells (LEECs) and optical devices for data record, storage and security . Therefore we believe this paper will attract more research interest and stimulate greater progress in the future.…”

Study of a phosphorescent cationic iridium(iii) complex displaying a blue-shift in crystals

“…20 Changes in the emission wavelength in the solid state is quite common especially looking at the neat solid (powder, neat thin film and crystal). The large majority of the cationic iridium(III) complexes display a bathochromic shift in solid state, 17,23,[32][33][34][24][25][26][27][28][29][30][31] whereas only few contributions report iridium(III) complexes displaying a hypsochromic shift. 17,27,40,[32][33][34][35][36][37][38][39] If bathochromic shifts could be easily rationalized with the presence of intermolecular interactions, such as - interactions, 14 blue shifted emission spectra in solid state are less straightforward dealing with neat solid.…”