Quantum Dot-Organic Oligomer Nanostructures: Electronic Excitation Migration and Optical Memory Design
- PDF / 195,425 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 57 Downloads / 184 Views
Q2.1.1
Quantum Dot-Organic Oligomer Nanostructures: Electronic Excitation Migration and Optical Memory Design Artjay Javier, C. Steven Yun, Geoffrey F. Strouse* Department of Chemistry, University of California, Santa Barbara CA 93106-9510 *[email protected] ABSTRACT Energy, in the form of an electronic excitation, can be directed within an inorganicorganic composite of semiconductor quantum dots and organic oligomers by manipulating the structural conformations of the organic component or the size of the inorganic component. Continuous-wave and time-resolved photoluminescence studies indicate that weak electromagnetic resonant coupling between discrete intra-chain and inter-chain excitations of the oligomer and quantum dot excitations can be used to produce a potentially useful optical display material. Thin film blends demonstrate a thermally-induced luminescence-detected chainmelting phenomenon that has the potential for writable optical memory. INTRODUCTION The energy and electron transport of hybrid organic-inorganic nanostructures composed of conducting polymers and semiconductor quantum dots has been well explored in optically stimulated1,2 and electrically pumped3,4 motifs. A combination of charge carrier transport5,6 and exciton diffusion has been found to be the predominant mechanisms for carrying electronic energy within these structures. The electronic excitation energy resonance between the quantum dot and polymer transitions is a prime factor in controlling the direction of energy flow. The size-dependent quantum-confined discrete optical transitions of semiconductor quantum dots7 allows for the tuning of this resonance through discrete control over the magnitude of the spectral overlap with organic oligomer excited states. Another layer of control can be exerted through the interactions of the organic oligomer component with itself, so-called “interchain excitations8,” which are common in solid-state organic thin films. These excitations have different energies and lifetimes9 than the isolated oligomer and therefore interact differently with the quantum dot excited states. With these in mind, it is conceivable to construct any emitted light color with the proper choice of component size and geometry. These complex interactions can be exploited to construct a device which has the potential for optical-based memory applications. Heating a disordered array of oligomer species can induce them to adopt more thermodynamically favorable conformations such as the formation of chain-aligned states. The addition of quantum dots as dopants into this oligomer matrix does not disrupt the local order, but serve as traps for migrating electronic excitations. An appropriate system can then be engineered whereby upon optical excitation of the organic oligomer the flow of electronic energy can be directed to the quantum dot to produce a continuum of desirable colors. Such a system is presented here, where we are able to form compact micron-scale tightly-assembled quantum dot structures that are very photo-stable.
Data Loading...
