Novel four-pyridylbenzene-armed biphenyls as electron-transport materials for phosphorescent OLEDs

A series of four-pyridylbenzene-armed biphenyl derivatives were designed and synthesized as an electron-transport and exciton- and hole-block layer for the fac-tris(2-phenylpyridine)iridium (Ir(PPy)3)-based green phosphorescent organic light-emitting devices (OLEDs), giving improved efficiency in comparison to that with both the electron-transport layer of tris(8-hydroxyquinoline)aluminum (Alq3) and the exciton- and hole-block layer of 2,9-dimethyl-4,7-diphenylphenathroline (BCP).     

A single-molecule excimer-emitting compound for highly efficient fluorescent organic light-emitting devices

A pyrene-containing single-molecule excimer-emitting compound, 1,8-bis(pyren-2-yl)naphthalene (BPyN), was synthesized. With BPyN as a host emitter, C545T-based green OLEDs were fabricated, exhibiting high efficiencies of 22 lm W(-1), 22 cd A(-1) and 6.2% external quantum efficiency (EQE) at 100 cd m(-2), and 19 lm W(-1), 22 cd A(-1) and 6.2% EQE at 1000 cd m(-2).     

Photocontrolled magnetization of CdS-modified Prussian blue nanoparticles

The first photocontrollable magnetic nanoparticles containing CdS and Prussian blue (PB) have been created using reverse micelles as nanoreactors. Photoinduced electron transfer from CdS to PB in the reverse micelle changed the magnetic properties of the composite nanoparticles from ferromagnetic to paramagnetic. The magnetization in the ferromagnetic region below 4 K was substantially decreased after UV light illumination and could be restored almost to its original level by thermal treatment at room temperature. This novel strategy of designing composite nanoparticles containing photoconductive semiconductors and magnetic materials to create photoswitchable magnetic materials may open many possibilities in the development of magneto-optical devices.     

Robust Spirobifluorene Core Based Hole Transporters with High Mobility for Long-Life Green Phosphorescent Organic Light-Emitting Devices

Using a tailored high triplet energy hole transport layer (HTL) is a suitable way to improve the efficiency and extend the lifetime of organic light-emitting devices (OLEDs), which can use all molecular excitons of singlets and triplets. In this study, dibenzofuran (DBF)-end-capped and spirobifluorene (SBF) core-based HTLs referred as TDBFSBF1 and TDBFSBF2 were effectively developed. TDBFSBF1 exhibited a high glass transition temperature of 178 °C and triplet energy of 2.5 eV. Moreover, a high external quantum efficiency of 22.0 %, long operational lifetime at 50 % of the initial luminance of 89,000 h, and low driving voltage at 1000 cd m⁻² of 2.95 V were achieved in green phosphorescent OLEDs using TDBFSBF1 . Further, a high-hole mobility μ_h value of 1.9×10⁻³ cm² V⁻¹ s⁻¹ was recorded in TDBFSBF2 . A multiscale simulation successfully reproduced the experimental μ_h values and indicated that the reorganization energy was the primary factor in determining the mobility differences among these SBF core based HTLs.