Electroluminescence Driven by Alternating Current: Materials and Devices
Sung Hwan Cho, Juhan Lee, Seong Soon Jo, Ihn Hwang and Cheolmin Park
Electroluminescent (EL) devices based on alternating current (AC) electric fields have a long-standing history and have been extensively studied with their great potential for applications in displays, sensors, and lighting. Insulating layers inserted between top and bottom electrode of a vertically stacked device result in the unique light-emitting principle of carrier generation and recombination. Most common AC EL devices with inorganic phosphors consist of simple consecutive stacks of four component layers: transparent bottom electrode/insulating layer/emissive layer/top electrode. When additional insulating layers were inserted between the emissive layer and top electrode, light emission was solely field-driven. The article presents the recent research development not only in understanding the fundamentals of AC driven light emission but also in improving the device performance for practical implementation such as brightness, operation voltage, power efficiency and color mixing and tuning. An emphasis is made on AC EL devices containing organic and organic/inorganic hybrid emission layers, in particular, fabricated by solution-based processes.
Keywords: Alternating Current (AC), Electroluminescence, Inorganic phosphors, Organic and polymer light emission, Colloidal quantum dots, Field induced electroluminescence