Degradation of OLED performance by exposure to UV irradiation

Abstract

Organic light-emitting diode (OLED) displays are highly susceptible to the harsh environmental conditions found outdoors, like exposure to direct sunlight as well as UV radiation and storage temperature, resulting in a loss of luminance and lifespan, pixel shrinkage, and permanent damage and/or malfunction of the panel.Here, we fabricated top emission OLEDs (TEOLEDs) using Yb : LiF (1 : 1, 2 nm)/Ag : Mg (10 : 1, 16 nm) andMg : LiF (1 : 1, 2 nm)/Ag : Mg (10 : 1, 16 nm) cathode units and the performances of the devices were investigated by subjecting them to UV radiation. A fabricated red TEOLED (control device), employing a standard Mg : LiF (1 : 1, 2 nm) electron injection layer (EIL) and an Ag : Mg (16 nm) cathode, showed a rapid decrease in luminance and a fast increase in driving voltage at 10 mA cm À2 over time after UV irradiation for 300 h. However, a cathode unit comprising a Yb : LiF (1 : 1, 2 nm) EIL and an Ag : Mg (10 : 1, 16 nm) cathode showed no loss of luminance or increase in driving voltage at 10 mA cm À2 over time after UV irradiation for 300 h. Therefore, we investigated the changes occurring in both cathode units due to UV irradiation using the lift-out FIB-TEM technique and EDS mapping. With UV irradiation for 300 h, Ag atoms migrated toward the center of the cathode, Mg atoms migrated toward the CPL, and no Mg atoms were observed in the EIL area. In contrast, we observed (i) no substantial migration of Ag atoms and they were located at the center of the cathode, (ii) no migration of Mg atoms toward the CPL layer, and (iii) no movement of Yb atoms after UV irradiation. Furthermore, the UV irradiated red TEOLED with an Mg : LiF (1 : 1, 2 nm) EIL showed (i) deterioration in electron injection into the emissive layer (EML) and an increase in the EIL/metal interface resistance, and (ii) a remarkable shift of the J-V curve to the higher voltage side, while almost no such changes were observed in the TEOLD with a Yb : LiF (1 : 1, 2 nm) EIL. Also, an almost identical RGB pixel emitting area was noticed in the Yb : LiF (1 : 1, 2 nm) based devices after UV irradiation for 300 h. These results suggest that Yb could become a good candidate for the cathode unit, providing better device stability against harsh environmental conditions as well as excellent electron injection properties.

Retracted Article: Wavelength modulation of ZnO nanowire based organic light-emitting diodes with ultraviolet electroluminescence

“…Recently, organic light emitting diodes (OLEDs) have been extensively studied for their various advantages such as solution-processability, cost-effectiveness, and room temperature processing. [1][2][3][4][5][6] In particular, due to their capability of emitting high-energy ultraviolet (UV) light, high-efficiency UV-OLEDs demonstrate great signicance for IT storage, photocuring, aerospace, medical and military applications. 7,8 In addition, UV-OLEDs can be potentially implemented in RGB screens.…”

Ultraviolet Light Debondable Optically Clear Adhesives for Flexible Displays through Efficient Visible‐Light Curing

“…The exposure was set at ≈4200 mJ cm −2 , a level deemed appropriate to prevent damage to the underlying display panel of the device. [ 49 ] For the OCA film without any BP, UV exposure did not lead to any decrease in adhesion. However, in line with expectations, the four films containing BP showed a notable decrease in adhesion, as seen in Figure 2c.…”

A review of geometric and structural design for reliable flexible electronics

“…Therefore, externally attached flexible electronics are likely to be exposed to various environmental stimuli such as humidity, gas, and temperature, as well as the strain introduced in the previous chapter. Humidity, gas, and temperature affect the electrical and chemical characteristics of electronics, such as electrical conductivity, luminous efficiency, and gas response, resulting in changes of a flexible electronics' performance [102][103][104][105][106][107][108][109]. In addition, the low gas permeability of flexible electronics can cause problems such as infections when used on the skin of a human body, further limiting its applications [110][111][112][113].…”