Nanowerk April 18, 2024
Emerging light-emitting electrochemical cells (LECs) can be cost- and energy-efficiently fabricated by ambient-air printing by virtue of the in situ formation of a p-n junction doping structure. However, the in situ doping transformation renders a meaningful efficiency analysis challenging. Researchers in Sweden have developed a method for separation and quantification of major LEC loss factors, notably the outcoupling efficiency and exciton quenching. They found the shift in the position of the emissive p-n junction in common singlet-exciton emitting LECs to shift markedly with increasing current, and the influence of this shift on the outcoupling efficiency was quantified. They verified that the LEC-characteristic high electrochemical-doping concentration rendered singlet-polaron quenching (SPQ) was already at low drive current density, but also that SPQ increased super-linearly with increasing current, because of increasing polaron density in the p-n junction region. This resulted in SPQ dominating singlet-singlet quenching for relevant current densities, and significantly contributed to the efficiency roll-off. According to the researchers their method for deciphering the LEC efficiency roll-off can contribute to a rational realization of all-printed LEC devices that are efficient at high luminance… read more. Open Access TECHNICAL ARTICLEÂ
a) Schematic presentation of the optical interference between two light rays that originate from the same spot… Credit: Advanced Materials, 11 January 2024