Current status of electrophosphorescent device stability

Degradation Mechanisms and Reactions in Organic Light-Emitting Devices

“…123,124 It is noteworthy that other OLED architectures like inverted structures or OLEDs with transparent top contacts often exhibit lower lifetimes than their conventional counterparts. 77 This might be caused by the differences in charge carrier injection as well as the damage that may occur during device fabrication, especially by sputter deposition techniques for transparent top contacts. 125−127 During the last two decades, a wide range of different mechanisms of OLED degradation were suggested.…”

“…136 To obtain reasonable lifetime values, water vapor permeability rates (WVTR) better than 5 × 10 −6 g/m 2 /d and oxygen transmission rates (OTR) lower than 10 −3 cm 3 atm/m 2 /d are an absolute need for OLEDs as well as other organic optoelectronic devices like organic solar cells (OSCs). 77,215,264 Inorganic TFTs, for example, only need sealing conditions of about 10 −3 −10 −1 g/m 2 /d WVTR, whereas organic TFTs are expected to be more sensitive. 265 The transmission values required for OLEDs are several orders of magnitude lower than what is reached with conventional sealing techniques, used, for example, for liquid crystal displays and food packages.…”

“…Besides the damage of the underlying layers (by any kind of irradiation) during possible sputtering, 127 inverted samples show usually significantly lower lifetimes. 77 Another important point to consider is the location of the recombination zone. 72 From our analytical work, we know that many phosphorescent emitter materials react with neighboring HBL materials under OLED operation, mainly when the emission zone is located at this interface.…”

Diffusion of atmospheric gases into barrier-layer sealed organic light emitting diodes

“…Analysis of accelerated storage tests shows that a single mechanism of diffusion along interfaces can account for both modes in both transparent OLEDs ͑TOLEDs͒ and bottom-emitting OLEDs ͑BOLEDs͒. 7 Information derived from measurements and tests includes the lag time t ᐉ,x evident in Fig. 2͑b͒, the rates of growth of dark areas ͑−dA OLED / dt͒ that are taken from Figs.…”

Efficient red organic light-emitting diode sensitized by a phosphorescent Ir compound

“…Subsequently, Chen and co-workers [10] also obtained high efficiency and long lifetime pure red OLEDs by codoping Rubrene and DCJTB in Alq 3 , where the Rubrene was also used as the host together with Alq 3 . Simultaneously, the phosphorescence materials used as emitter or sensitizer to improve the EL efficiencies of red OLEDs by doping or codoping have also been reported [11][12][13][14][15]. However, the complicated device structure and the rapid decrease of EL efficiency at high current density affect severely the device stability in practical application, and the efficiencies of red OLEDs are still needed to further improve, especially, the EL efficiency at higher current density.…”