Colloidal II-VI semiconductor nanocrystals (NCs) are of increasing interest because of their potential applications as optoelectronic, photochemical, and nonlinear optical materials as well as biological labeling. The electronic and optical properties of these semiconductor NCs are controlled by their size, shape, surface, and surrounding environment. The capability to systematically manipulate the size and shape of the NCs remains an important goal of modern material science and technology. In this paper, we report the synthesis of colloidal dot-, rod- and tetrapod-shaped CdTe nanocrystals (NCs). The obtained NCs are characterized by transmission electron microscopy, Raman and X-ray diffraction spectra. Both the dot- and rod-shaped NCs are of zinc-blende phase whereas the tetrapod-shaped NCs are a mixture of zinc blende and wurtzite structures. It is proposed that the concentration of stacking faults forming during NCs' growth plays an important role in the geometry of CdTe NCs.
Organic electroluminescent devices have received considerable attention due to their application in flat-panel displays. To achieve full-color displays, it is necessary to obtain organic layers emitting red, green, and blue light, but it is still a challenge to obtain efficient and stable organic layer emitting red light so far. Recently, we found that an organic salt, trans-4-[p-[N-ethyl-N-(hydroxyethyl)amino]styryl]-N-methylphridinium tetraphenylborate (ASPT), exhibits efficient red-light emission. In this paper, we report a multilayer electrolumicescent device incorporating a hole-transport layer, an ASPT layer, and an electron-transport layer. The dependence of the carrier transport and the luminescence on the device structure is investigated in detail. Compared to the monolayer device, the balance between hole and electron injections is significantly improved for the multilayer device, and thus the electroluminescent efficiency and intensity are enhanced.