At low voltages emission from the CdSe layer occurs. Close matching of the emitting layer of nanocrystals with the work function of the metal contact leads to an operating voltage11 of only 4V. Light emission arises from the recombination of holes injected into a layer of semiconducting p-paraphenylene vinylene (PPV)8-10 with electrons injected into a multilayer film of cadmium selenide nanocrystals. By taking advantage of developments in the preparation and characterization of direct-gap semiconductor nanocrystals4-6, and of electroluminescent polymers7, we have now constructed a hybrid organic/inorganic electroluminescent device. This independent control of mobility and conductivity allows the realization of oligomer-based thin-film transistors showing characteristics close to those of classical a-Si:H-based thin-film transistors.ĮLECTROLUMINESCENT devices have been developed recently that are based on new materials such as porous silicon1 and semiconducting polymers2,3. Besides which, conductivity in thin films of conjugated oligomers is mainly determined by the purity of the materials, allowing values lower than 10-7 S cm-1. to the decrease of grain boundaries, leading to values close to 10-1 cm2 V-1 s-1, comparable to that of amorphous hydrogenated silicon. It is thus shown that carrier mobility is directly related to the long range structural order in these films, i.e. On the other hand, conjugated oligomers are well-defined materials, offering various physical and chemical ways of controlling the structural organization of thin films made out of them. This behaviour can be understood from the variable range hopping mechanism which describes charge transport in these materials. Conjugated polymers and other amorphous materials exhibit a low carrier mobility, of the order of 10-4-10-5 cm2 V-1 s-1, and all attempts to increase it through slight doping of the organic semioconductor have failed, owing to the existence of a direct relationship between mobility and conductivity. ![]() The mode of operation of these devices shows that a high carrier mobility together with a low conductivity are required. Various organic conjugated materials have been used as active semiconducting layers in thin-film transistors. Realizing stable dispersion of silicon particles in water. Improving the electrical properties of the quantum dot, and for The process is promising forĪttaching short molecules to the particle surface, necessary for Various molecules have been successfully reacted with the siliconĬrystals in the gas-phase, and a silicon ink can be readily obtained In-flight plasma initiated passivation scheme described in this thesis. Reaction time and the use of solvents, are overcome by using the The disadvantages of the liquid phase passivation scheme, long The highest ensemble quantum yield ever reported for the case of Fluorescent quantum yields exceeding 60% have been measuredįor silicon inks with a peak emission wavelength around 800 run. Synthesis of a clear and stable colloidal dispersion of silicon Of plasma-produced silicon nanocrystals with 1-dodecene leads to the Hydrogen-terminated surface, which is an ideal chemical configurationįor grafting alkenes onto the particle surface. This behavior likely leads to the formation ![]() Temperature of very small clusters exceeds the gas temperature of The particle temperature exceeds theīackground gas temperature of approximately 100 K, and the instantaneous The silicon cluster with the surrounding plasma, in particular withĪrgon ions and with atomic hydrogen. Small crystallites has been investigated by studying the interaction of The mechanism leading to the formation of The system is capable of producing up to 50 Observation of intense visible photoluminescence when the particles areĮxcited by UV irradiation. The short residence time in the reactor (<10 ms), very smallĬrystallites are produced, and quantum confinement effects lead to the Resulting in the nucleation and growth of silicon nanoparticles. Quartz tube through which a silane containing mixture is flown, A novel reactor for the controlled synthesis of small silicon
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