Researchers from South China University of Technology developed a new OLED structure that promises to enable low-cost efficient fluorescent OLED devices. The so-called pn-OLED structure is inspired by p-n junction theory and inorganic LED design.
The pn-OLED uses a highly-efficient emission-layer-free OLED, in which the p-type and n-type organic semiconductors are sandwiched vertically between an ITO anode and a lithium fluoride/aluminum cathode. The luminescent center of the pn-OLED is located in the pn junction region. The light-emission behavior of this device is a result of the synergetic energy release from both the p-type and n-type materials. This is in contrast to conventional OLEDs, where the light generation occurs from single-molecule emitters.
The researchers say that this OLED structure has a potential to achieve extremely high efficiency - close to the theoretical maximum 100% internal quantum efficiency. pn-OLEDs also require low operating voltages, which results in very high power-conversion efficiencies. The researchers still need to investigate the operating mechanism of the pn-OLEDs, and also examine the underlying connections of the working principles of both organic and inorganic pn junction LEDs.