ABSTRACT
Materials of 1 to 100 nm in size are exhibiting new and unique electrical and optical properties. A more precise understanding of these properties is essential to overcome certain issues — particularly environmental development — facing current technology. Semiconductor nanocrystals (NCs), also known as quantum dots (QDs), are a typical nanomaterial, and their properties can be tuned by controlling their physical size (generally from 1 to 10 nm) [1]. These colloidal NCs offer several advantages for mass production, particularly their solution-based fabrication process, which is both simple and inexpensive [2]. QDs have been studied since the 1980s, and in 1993, the successful synthesis of highquality Cd chalcogenide QDs strengthened their basis in this ϐield
[3]. Since then, a variety of research has been reported on the effects of controlling the shape and composition of QDs, and the growth of high-quality NCs has been achieved [4]. Today, light-emitting diodes (LEDs) are an eco-friendly alternative to incandescent bulbs and ϐluorescent lamps in lighting technology. QDs can be excellent light source materials for LEDs because they have size-tunable monochromatic emission color, high quantum efϐiciency, and good thermal stability [5]. Although a considerable amount of research related to QD-LEDs has been actively performed, most of the results are preliminary analyses of basic methods. To fabricate QD-LEDs with high efϐiciency and durability, many other aspects require more elaborate consideration, including: synthesis of highly luminescent and stable non-toxic QDs, development of proper QD’s encapsulating material and efϐicient LED chips, improvement of LED’s structure for attaining higher light extraction efϐiciency, and so on. Hereby, our investigation will focus on following fundamental factors: the enhancement of QDs’ properties and the problems/ solutions of achieving commercialization for QD-LEDs. In Section 16.2, we discuss some general principles regarding QDs and controlled growth of QDs for adjusting their emission wavelength and intensity. In Section 16.3, we introduce the current status and issues concerning QD-LEDs, and then explain three important factors — toxicity, stability, and encapsulation — which must be addressed if QDs are to be utilized as wavelength converters for LEDs.
