Zinc oxides have attracted attention in high-temperature waste heat recovery due to their high melting points. This review aims to provide a comprehensive summary of the effects of dopant on thermoelectric properties of ZnO based bulk, thin films, nanowire as well as the effects of nanostructuring on ZnO based materials. In general, the thermoelectric performance can be enhanced by a single doping. Among single dopant elements, Al dopant seems to be effective dopant resulting in better thermoelectric properties. However, the solubility limit of the dopant in single doping limits the improvement of thermoelectric performance. Efforts in dual doping to improve the thermoelectric properties of ZnO materials have been conducted. As a result, the drastic improvement of the thermoelectric performance from Al-Ga dually doped ZnO bulk and Ga-In dually doped ZnO thin films shows strong evidence of this approach. In addition to doping effects, the thermoelectric performance can also be enhanced through structural effects such as mismatches between the film and substrate, morphology, thermal treatments or introducing nano-precipitated materials. In addition, the low-dimensional structure such as nanowire structure is promising for improving the thermoelectric properties of materials because of their strong quantum confinement effect. This leads to the increase of the Seebeck coefficient according to the Mott's relationship without lowering the electrical conductivity.
maximum 250 words) Magnetic nanoparticles (MNPs) exhibiting superparamagnetic properties might generate large magnetic dipole-dipole interaction with electron spins in organic semiconductors (OSECs). This concept could be considered analogous to the effect of hyperfine interaction (HFI). In order to investigate this model, Fe3O4 MNPs are used as a dopant for generating random hyperfine-like magnetic fields in a HFI-dominant π-conjugated polymer host, poly(2-methoxy-5-(2ethylhexyloxy)-1,4-phenylenevinylene) (MeH-PPV). The magnetoconductance (MC) response in organic light emitting diodes made by MeH-PPV/MNP blends is used to estimate the effective hyperfine field in the blends. Firstly, we find that the shape of the MC response essentially remains the same regardless of the MNP concentration, which is attributed to the similar functionality between the nuclear spins and magnetic moments of the MNPs. Secondly, the width of the MC response increases with increasing MNP concentration. Magneto-optical Kerr effect (MOKE) experiments and micromagnetic simulation indicate that the additional increase of the MC width is associated with the magnetization of the blend. Finally, the MC broadening has the same temperature dependent trend as the magnetization of the MNPs where the unique effect of the MNPs in their superparamagnetic and ferromagnetic regimes on the MC response is observed. Magneto-photoinduced absorption (MPA) spectroscopy confirms that the MC broadening is not due to defects introduced by the MNPs but a result of their unique superparamagnetic behavior. Our study yields a new pathway for tuning OSECs' magnetic functionality, which is essential for organic optoelectronic devices and magnetic sensor applications.Keywords: organic semiconductor, magnetic nanoparticle, magnetic field effect, hyperfine interaction, coherent spin mixing rate.Recently, there has been interest in coherent spin manipulation via controlling of the HFI by several state-of-the-art methods, including isotope exchange with different nuclear spins and pulsed electron-nuclear double resonance (ENDOR) spectroscopy. 13-15, 30, 35-38 The former method chemically replaces particular atoms in the molecule by atoms with different nuclear spins. [13][14][35][36][37] In conventional conducting polymers, the presence of new isotopes, e.g. 2 H and 13 C, significantly
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