Chapter 19 - Solution-processed light-emitting devices

Abstract

Solution-processed electrically driven light-emitting devices have applications in different sectors including display technology, solid-state lighting, sensor, etc. The most studied light-emitting devices are in diode geometry, commonly called light-emitting diodes (LEDs). However, it is possible to fabricate a light-emitting transistor (LET) that exhibits switching property of the device in addition to its light emission. Solution-processed, printable thin-film LEDs and LETs are commonly fabricated by using high-luminance polymers and colloidal quantum dots (QDs). Nowadays, the quantum efficiency of solution-processed red and green LEDs has increased by more than 20% with the highest luminance >10,000cd/m2, which is good enough for commercial use, while there are some critical issues to the high-efficiency blue LEDs . Besides, the stability of solution-processed LEDs is a big concern over conventional vacuum-deposited LEDs. Fabrication of multilayer LETs is another challenging issue which is required to achieve balance and efficient charge injection to the emissive layer of the device. Compared to LEDs, LETs have more serious issues to resolve. The key factors of LETs are their poor quantum efficiency and lower brightness. This chapter - discuss different stages of developments of solution-processed LED and LET devices, their advantages and disadvantages, and their prospects.