Nanoconfinement induced electroluminescence spectrum shift in organic light-emitting diodes

The demands for nanoscale organic light-emitting diodes (OLEDs) have been intensively increased due to theirs' lightweight, flexibility, which is critical for next-generation displays. Although nanoscale OLEDs are ideal solutions for ultra-high-resolution displays, there are few related researches have been reported. Here we design and fabricate a series of nano-hole array OLEDs (NAOLEDs) with the pixel size from 160 nm to 10,000 nm, based on which, the electroluminescence (EL) spectral properties are systematically studied. It is found that the EL spectral peak produces a red shift and full width at half maximum (FWHM) increases with the decrease of the NAOLED pixel size under the same bias, while a blue shift as well as reduced FWHM are observed with the increase of bias voltage for the same pixel size of the NAOLED. The existence of exciton and exciplex generated from the different combination area is the critical reason of the spectrum change in the NAOLED, which is further verified by multiple fluorescence properties measurement. This research reveals basic principle of nano-confinement induced EL spectral properties change in the NAOLEDs which should heavily impact next-generation OLED and their applications in multi-functional systems, smart sensors, and electronic displays, etc.