•Diphenylamine modified IrIIIbis(phenylpyridinato)-4-carboxylpicolinate was synthesized.•Diphenylamine influenced absorption energy and orbital electron density distribution.•Conversion efficiency of 2.51% and open circuit voltage of 0.68 V was achieved.The new complex IrIIIbis(4-diphenylaminophenylpyridinato)-4-carboxylpicolinate (complex 3) tailored by electron-donating diphenylamine (DPA) was synthesized and characterized for dye-sensitized solar cells (DSSCs) application. The introduction of the DPA moiety to phenylpyridine ligand makes the absorption bands of the complex 3 extend to 650 nm, and adjusts the highest occupied molecule orbital to be mainly localized on DPA-ppy (diphenylaminophenylpyridine) ligands (accounting for 74.44% for one DPA-ppy ligand) while the lowest unoccupied molecule orbital to be lied on the pic (pyridine-2,4-dicarboxyl acid) moiety (96.80%). TD-DFT calculation further shows the charge-transfer transitions from ligand DPA-ppy and Ir atom to the pic anchoring moiety principally contribute to the absorption bands of the complex 3 in the visible region, which is well beneficial to electron injecting into TiO2 film. For DSSCs using complex 3 as sensitizer, the energy conversion efficiency is up to 2.51%, with a short circuit current density of 7.51 mA/cm2 and an open circuit voltage of 0.68 V. These results indicate that it is possible for IrIII complex to achieve more efficient cell parameters if more rational IrIII complexes are developed.The diphenylamine was introduced to IrIIIbis(phenylpyridinato)-4-carboxylpicolinate to improve light-harvesting capacity of the resulting complex and induce favorable orbital electron density distribution for electron-injecting into TiO2 film when used as photosensitizer of dye-sensitized solar cells. As a result, a 2.51% conversion efficiency and 0.68 V open circuit voltage was achieved.

In this article, we reported the synthesis and characterization of a novel silafluorene-based host material, 1,3-bis(5-methyl-5H-dibenzo[b,d]silol-5-yl)benzene (Me-DBSiB), for blue phosphorescent organic light-emitting devices (PHOLEDs). The Me-DBSiB was constructed by linking 9-methyl-9-silafluorene units to the phenyl framework through the sp3-hybridized silica atom to maintain high singlet and triplet energy, as well as to enhance thermal and photo-stability. The calculated result shows that the phenyl core does not contribute to both the highest occupied molecular orbital and lowest unoccupied molecular orbital. Wide optical energy gap of 4.1 eV was achieved. When the Me-DBSiB was used as the host and iridium (III) bis[(4,6-difluorophenyl)pyridinato-N,C2′]picolate (Firpic) as the guest, a maximum current efficiency was 14.8 cd/A, lower than the counterpart of 1,3-bis(9-carbazolyl)benzene (28 cd/A). The unbalanced barrier for electron and hole injection to host layer may be responsible for low efficiency. Even so, our results show that silafluorene moieties are promising building blocks for constructing wide-energy-gap host materials.

Iridium complexes with dicyanovinyl-grafted phenylpyridine/1-phenylisoquinoline as ligands are synthesized and their photophysical, electrochemical, and sensitization properties in DSSCs are investigated. The iridium complexes present significantly enhanced absorption from 400 to 525 nm. The 1-phenylisoquinoline-based iridium complex show bathochromic-shift emission in DMSO solution compared with their phenylpyridine-based counterpart, while their absorption response and photoluminescence peak in solid show little difference despite extension of the conjugated system. Using DSSCs, the conversion efficiency of 0.62% and open-circuit current of 1.4 mA/cm2 is achieved. The poor performance is attributed to the excited-state properties of iridium complexes according to the TD-DFT calculation.

A series of 2-vinylpyridine-type platinum(II) complexes bearing different main-group blocks (B(Mes)2, SiPh3, GePh3, NPh2, POPh2, OPh, SPh, and SO2Ph, where Mes = 2-morpholinoethanesulfonic acid) were successfully prepared. As indicated by the X-ray single-crystal diffraction, the concerned phosphorescent platinum(II) complexes exhibit distinct molecular packing patterns in the solid state to bring forth different interactions between individual molecules. The photophysical characterizations showed that the emission maxima together with phosphorescent quantum yield of these complexes can also be affected by introducing distinct main-group moieties with electron-donating or electron-withdrawing characters. Furthermore, these 2-vinylpyridine-type platinum(II) complexes exhibit markedly different photophysical and electrochemical properties compared with their 2-phenylpyridine-type analogues, such as higher-lying highest occupied molecular orbital levels and lower-energy phosphorescent emissions. Importantly, these complexes can show good potential as deep red phosphorescent emitters to bring attractive electroluminescent performances with Commission Internationale de L’Eclairage (CIE) coordinates very close to the standard red CIE coordinates of (0.67, 0.33) recommended by the National Television Standards Committee. Hence, these results successfully established structure–property relationship concerning photophysics, electrochemistry, and electroluminescence, which will not only provide important information about the optoelectronic features of these novel complexes but also give valuable clues for developing novel platinum(II) phosphorescent complexes.

•Iridium complexes with 5,5-dimethyl-3-(pyridine-2-yl)cyclohex-2-enone were synthesized.•The absorption response to low energy band was extended and the emission of deep red was realized.•A wide spectral range (350–675 nm) and open-circuit voltage of 645 mV was presented using for DSSC.The three iridium complexes based on 5,5-dimethyl-3-(pyridine-2-yl)cyclohex-2-enone ligand and pyridine-2,4-dicarboxyl acid (5b) or 2,2′-bipyridine-4,4′-dicarboxyl acid (5c) as ancillary anchoring ligands were synthesized and characterized as potential photosensitizer for dye-sensitized solar cells (DSSC). Using of cyclohexenone derivates as ligands extended the absorption response of the iridium complex to low energy band near 550 nm and shifted the maximum emission peak to deep red (near the 680 nm). The theoretical molecular orbital calculations shows that the HOMO orbitals of all the complexes are contributed by the combination of orbitals on Ir atom (about 50%) and π orbitals located on 5,5-dimethyl-3-(pyridine-2-yl)cyclohex-2-enone. While auxiliary ligands with anchoring group exclusively contribute to electron density of the LUMO orbital, accounting for 96.33% in 5b and 95.51% in 5c. It is beneficial for electron injection in DSSC application. Applying them to DSSC, the IPCE response of the DSSCs covered a wide visible spectral range from 350 to 675 nm and the cells presented an open-circuit voltage of 645 mV, a power conversion efficiency of 1.03%.