Improving operation lifetime of OLED by using thermally activated delayed fluorescence as host

We fabricated organic light-emitting diodes (OLEDs) with the thermally activated delayed fluorescence (TADF) material of 4CzIPN, which show better stability compared with the 4,4’-Bis(carbazol-9-yl)biphenyl (CBP) based devices. The half lifetime of the device using 4CzIPN as host material has doubled, and a slower voltage rise compared with that of CBP-based devices has been achieved, which indicates the improvement of stability. We attribute the better stability to the good film morphology and difficult crystallization property of 4CzIPN. Our results suggest that employing the 4CzIPN as host material can be a promising way of fabricating OLEDs with longer operation lifetime.     

Research on the impact of spin coating silver nano clusters on the performance of OLED devices

To achieve uniform distribution of silver nano clusters (SNCs) on substrate and reveal its effect on the performance of organic light-emitting diode (OLED), the SNCs incorporated OLED was fabricated and SNCs were coated by multi-step spin coating. Compared with the device without SNCs film, the brightness and current efficiency of the OLED devices with SNCs film were highly raised. The enhancement is attributed to SNCs induced local surface plasmon (LSP) oscillation, which can increase the radiative rate of excitons on Alq₃ molecules.     

Transparent conductive PVP/AgNWs films for flexible organic light emitting diodes by spraying method

In this study, a simple spraying method is used to prepare the transparent conductive films (TCFs) based on Ag nanowires (AgNWs). Polyvinylpyrrolidone (PVP) is introduced to modify the interface of substrate. The transmittance and bending performance are improved by optimizing the number of spraying times and the solution concentration and controlling the annealing time. The spraying times of 20, the concentration of 2 mg/mL and the annealing time of 10 min are chosen to fabricate the PVP/AgNWs films. The transmittance of PVP/AgNWs films is 53.4%—67.9% at 380—780 nm, and the sheet resistance is 30 Ω/□ which is equivalent to that of commercial indium tin oxide (ITO). During cyclic bending tests to 500 cycles with bending radius of 5 mm, the changes of resistivity are negligible. The performance of PVP/AgNW transparent electrodes has little change after being exposed to the normal environment for 1 000 h. The adhesion to polymeric substrate and the ability to endure bending stress in AgNWs network films are both significantly improved by introducing PVP. Spraying method makes AgNWs form a stratified structure on large-area polymer substrates, and the vacuum annealing method is used to weld the AgNWs together at junctions and substrates, which can improve the electrical conductivity. The experimental results indicate that PVP/AgNW transparent electrodes can be used as transparent conductive electrodes in flexible organic light emitting diodes (OLEDs).