New strategy for efficient OLED active matrix displays

Now Dr. Zhongbin Wu, Dr. Yuan Liu, and PhD student Erjuan Guo present the first electronic device that combines a vertical organic permeable base transistor (OPBT) and an OLED. With this novel device concept of an organic permeable base light-emitting transistor (OPB-LET), the researchers succeeded in combining the function of a highly efficient switching transistor and an organic light-emitting diode as commonly employed in active matrix displays. Active matrix liquid crystal displays (AMLCD) usually contain a matrix of thin-film transistors to drive LCD pixels. Each individual pixel has a circuit with active components (mostly transistors). In this context, organic light-emitting transistors, three-terminal devices combining a thin-film transistor with a light-emitting diode, have generated increasing interest. However, increasing their efficiency while keeping the operating voltage low remains a key challenge.

"The key to construct the high performance OPB-LETs is the permeable base electrode located at the center of the device, forming a distinctive optical microcavity and regulating charge carrier injection and transport. The thus designed three-terminal vertical optoelectronic devices can simultaneously high efficiencies (up to 24.6%), high luminance (up to 12,513 cd m-2), and low driving voltages (<5.0 V)," explains Erjuan Guo.

The performance of OPB-LETs demonstrated in this work is comparable to state-of-the-art OLEDs and cutting-edge, low-voltage organic transistors. Prof. Karl Leo explains: "We expect that this novel device principle will pave the way for highly-efficient flexible displays with a rather simple pixel design."