The luminescence of inorganic core-shell semiconductor nanocrystal quantum dots (QDs) can be tuned through the visible and near infrared spectral range by changing the size and material of the QDs while preserving a narrowband, gaussian emission spectrum and photoluminescence efficiency of 25%. Organic capping groups, surrounding the QD lumophores, facilitate processing in organic solvents and their incorporation into organic thin film light emitting device (LED) structures. Recent reports have shown that hybrid organic/inorganic QD-LEDs can be fabricated with high brightness and small spectral FWHM, utilizing a phase segregation process which self-assembles QDs onto an organic thin film surface [Coe et al., Nature 420, 800 (2002)]. The phase segregation process can be generally applied to the fabrication of QD-LEDs containing a wide range of particle sizes and materials. QD-LEDs emitting from 540 nm to 1,550 nm have been demonstrated to date, with external quantum efficiencies of thin film light emitters. Organic light emitting devices (OLEDs) have been identified as a dominant new technology poised to realize the next generation of flat panel displays. OLED performance is exemplified by wide viewing angles, high color contrast, and low power consumption as compared to emissive liquid crystal displays. Indeed, internal quantum efficiencies can approach 100% when organic phosphorescent molecules are used as the emitting materials. A significant challenge of today's OLED technology remains the identification and synthesis of organic lumophores compatible with electrically pumped device structures. Only a handful of efficient and long-lived organic phosphors have been incorporated into laboratory devices, while the ongoing research is aimed at the chemical design of new molecules, especially in the blue part of the spectrum. As such, inorganic quantum dots have generated interest in the OLED community as efficient alternative lumophores, whose saturated color emission can be tuned across the visible spectrum. Additionally QD-LEDs provide an accessible platform for investigating physical processes in hybrid organic/inorganic structures.
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