양자점을 포함한 복합체의 제작과 응용

Abstract

Colloidal semiconductor nanocrystal quantum dots (QDs) are being extensively studied to exploit their unique properties including the zero-dimensional discrete electronic energy feature, high photostability, tunable and bright emission, and solution processibility. They can promise many potential applications including biological fluorescent probes, light emitting diodes (LEDs), lasers, and solar cells. Before QDs being actively applied to many device applications, they often need to be stably embedded in an appropriate matrix. Polymers or inorganic matrices can be used to fabricate QD embedded composites. This thesis introduces simple in-situ fabrication of QD embedded inorganic or organic materials and their applications. Strongly luminescent and highly loaded CdSe QD-silica derivative composite films are prepared by simple one-step method. QDs are grown in situ with the inorganic silica matrix formation using spin-on-glass organosiloxane polymers. Emissions from the QD-silica composites are bright as ~ 8 % quantum efficiency (QE). Loading fraction of QDs in the composite is achieved to 13%. in-situ QD synthesis in silica shows similar behavior to solution phase synthesis and the lifetime study shows luminescence from the QD-silica composites are not the defect mediated emissions but the resonant excitonic emissions. A QD-silica composite capped LED is fabricated to demonstrate down-conversion pseudo white illumination. CdSe QD-P3HT composite films are prepared by in-situ QD synthesis in organic poly(3-hexylthiophene-2,5-diyl) (P3HT) polymer. Tributylphosphine (TBP) or triphenylphosphine (TPP) are used for surfactants or selenium precursor coordinating molecules. Applications to solar cells for these two kinds of fabrication manners are achieved. TEM analysis shows the in-situ synthesis of QDs in P3HT polymers, but QD fractions in solar cell devices are lower than composites prepared by the blending method of P3HT and as-prepared QDs. The composite devices that are made with TBP have three times of power conversion efficiency (PCE) than the devices which are fabricated with P3HT only.