Homoleptic Ir Complexes Research Articles

All-small-molecule organic solar cells based on cyclometalated tris-Ir(III) complexes as donor materials

Cyclometalated tris-Ir(III) complexes with six-coordinated octahedral configuration are beneficial to reduce aggregation for improved film morphology in organic solar cells (OSCs). Herein, two homoleptic tris-Ir complexes of eBz3Ir and eTBz3Ir showing majority absorption from UV to light-blue range are designed as electron donor materials. Owing to the extended π-conjugation by an extra thiophene ring in each ligand, eTBz3Ir exhibits red-shifted and stronger absorption as well as better charge transport property than eBz3Ir. Therefore, when employing the fused-ring non-fullerene acceptor Y6 or L8-BO to fabricate all-small-molecule OSCs (ASMOSCs), eTBz3Ir blended devices demonstrate higher efficiency than eBz3Ir, with maximum power conversion efficiency (PCE) achieving at 9.48/7.55% for Y6 and 10.48/6.46% for L8-BO devices, respectively. To our knowledge, over 10% PCE is among the highest values for binary ASMOSCs based on organometallic Ir complexes as photovoltaic materials. Such uncompetitive solar-light absorption but relatively high PCE indicates homoleptic Ir complexes with octahedral configurations are expected as promising photoactive materials for high-efficiency ASMOSCs.

Synthesis and Photophysical Studies of Heteroleptic Tris-Cyclometalated Ir(III) Complex for Red OLED

The synthesis and photophysical study of efficient phosphorescent iridium(III) complex having two different (C∧N) ligands are reported. In order to improve the luminescence efficiency by avoiding triplet–triplet (T–T) annihilation and study luminescent mechanism of the heteroleptic iridium complex, Ir(piq-3F)2 (dpq-4F) is designed and prepared where piq-3F and dpq-4F represent 1-(4′-fluorophenyl)isoquinoline and 2-(3′-fluorophenyl)-4-phenylquinoline, respectively. We thought that both piq-3F and dpq-4F ligands can act as a source of energy supply because of the relative HOMO energy level and the luminescence lifetime of homoleptic Ir complexes Ir(piq-3F)3 Ir(dpq-4F)3. However the UV-vis absorption spectra and the PL spectra of Ir(piq-3F)2 (dpq-4F) is more similar to that of Ir(piq-3F)3. In spite of lower triplet energy level of dpq-4F, the excitation energy is not intramolecular transferred from two piq-3F ligands to one dpq-4F ligand. The luminescence occurs mainly at piq-3F ligand. It is due to the strong MLCT characteristic of piq-3F ligand. To analyze luminescent mechanism, we calculated these complexes theoretically by using computational method.