Effect of Organic Salt Doping on Electron Injection in Single-Layer Polymer Light-Emitting Diodes

Abstract

We report the effect of organic salt doping on the carrier injection in single-layer polymer light-emitting diodes (PLEDs). From the anomalous behavior in the luminance-voltage characteristic of the salt-doped devices with LiF layer, it was found out that the electron injection through LiF layer occurs competitively with the electrochemical n-doping near the cathode. After the completion of n-doping near the cathode, even without LiF layer the salt-doped devices exhibit the performance comparable to that of the conventional devices with LiF layer. At high operating voltages the salt-doped devices showed the higher brightness and better device stability compared with the conventional devices. We also report for the first time that the salt doping does not affect the device stability appreciably.

Organic Transparent Electrodes Applied to Polymer Light Emitting Diodes

“…• C for 10 min [23]. For blue light emission, poly(9,9-dioctylfluorene) (PFO) (American Dye Source Inc.) [24] was dissolved in toluene (1 wt%) and spin-coated on the prepared substrate at 1300 rpm for 30 s, and annealed at 80…”

Inverted Bottom-Emission Polymer Light-Emitting Devices Doped with Organic Salt

“…Meanwhile, the doping of an organic salt such as tetra-n-butylammonium tetrafluoroborate (Bu 3 NBF 4 ) has recently been reported for polymer light-emitting devices (PLEDs). [8][9][10][11][12] Salt-doped PLEDs are known to exhibit similar characteristics to frozen-junction light-emitting electrochemical cells (LECs). 10,11) As in the case of frozenjunction LECs which are insensitive to the electrode material, 13) salt-doped PLEDs work well with most electrode materials, without the need to carefully consider their work functions.…”