Highly efficient organic light-emitting diodes are in urgent demand in applications of new generation full-color displays and solid-state lighting sources. The limitation of device performance is greatly affected by extrinsic and intrinsic elements of the light out-coupling process. By elaborately designing emitters as sticklike molecules, horizontal orientation ratios in the range of 86–93% were realized to intrinsically increase the out-coupling factor of electroluminescence devices. These elongated compounds are inclined to lie parallel to substrate in vacuum-deposited thin solid films and regularize their transition dipole moments in a major degree. As consequences of such desirable molecule arrangement, remarkable external quantum efficiencies near 21% for pure blue devices, close to 30% for sky-blue devices, and over 35% for greenish blue devices were respectively achieved. A compatible strategy on devising high-performance emitters for organic electroluminescence is advocated herein.

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We have investigated the electronic structures of recently discovered superconductor FeSe by soft-x-ray and hard-x-ray photoemission spectroscopy with high bulk sensitivity. The large Fe 3d spectral weight is located in the vicinity of the Fermi level (EF ), which is demonstrated to be a coherent quasi-particle peak. Compared with the results of the band structure calculation with local-density approximation, Fe 3d band narrowing and the energy shift of the band toward EF are found, suggesting an importance of the electron correlation effect in FeSe. The self energy correction provides the larger mass enhancement value (Z −1 ≃3.6) than in Fe-As superconductors and enables us to separate a incoherent part from the spectrum. These features are quite consistent with the results of recent dynamical mean-field calculations, in which the incoherent part is attributed to the lower Hubbard band.

Up until now there has been no direct method for detecting the electronic and magnetic structure of each atomic layer at the surface, which is an essential analysis technique for nanotechnology. For this purpose, we have developed a new method, diffraction spectroscopy, based on the photon energy dependence of the angular distribution of Auger electron emission. We have applied this method to analyze the magnetic structure of a Ni ultrathin film on a Cu(001) surface around the spin reorientation transition. Atomic-layer resolved x-ray absorption and magnetic circular dichroism spectra were obtained. Surface and interior core-level shifts and magnetic moments are determined for each atomic layer individually.