Management of charge carriers and excitons for efficient and color-stable white phosphorescent organic light-emitting diodes with simplified structure

Suppressing thermal quenching of lead halide perovskite nanocrystals by constructing a wide-bandgap surface layer for achieving thermally stable white light-emitting diodes

“…The stabilities of excitons are determined by external factors such as temperature and carrier concentration. [30][31] In this case, high temperature can lead to excitons decomposition and broadening of exciton absorption peak, resulting in fluorescence decay or even quenching. By comparison, when the temperature increased to 373 K, the exciton absorption peak of the pristine CsPbBr3 NCs became widened significantly, while the SO4 2--treated CsPbBr3 NCs still maintained the initial shape of the absorption peak (Figure 3ab).…”

Improvement of electro-optic performances in white organic light emitting diodes with color stability by buffer layer and multiple dopants structure

“…[9][10][11] Color stable and high efficient WOLEDs with doping structure are usually based on two kinds of device structures, including a single emitting layer with multiple dopants (SEML-MD), [12] and a multiple emitting layer with single dopant (MEML-SD). [13][14][15][16] Kim et al realized a high performance single emitting layer with three color dopant WOLED with a maximum luminance of 37810 cd/m 2 at 11 V and a luminous efficiency of 48.10 cd/A at 5 V, [12] but the emission is not stable with increasing driving voltage and it is not easy to precisely control the doping process for optimum doping concentration ratio among three dopants. [17] For the MEML-SD WOLED device, Chen and Han reported color-stable WOLED devices by using the mixed-host EML structure, which can alleviate the shift of recombination zone and obtain better charge balance, but CIE (1931) coordinates of their devices are far from the white light region.…”

“…[17] For the MEML-SD WOLED device, Chen and Han reported color-stable WOLED devices by using the mixed-host EML structure, which can alleviate the shift of recombination zone and obtain better charge balance, but CIE (1931) coordinates of their devices are far from the white light region. [13,14] Liu et al achieved a pure white OLED device with CIE coordinate of (0.33, 0.38) at a luminance of 10000 cd/m 2 by using a hybrid emitting structure, but the device shows a poor color stability, the CIE coordinate changes from (0.50, 0.42) to (0.33, 0.38) with the increase of luminance from 10 cd/m 2 to 10000 cd/m 2 . [15] Hence, high efficiency and color stability WOLEDs with simplified structure and easy fabrication should be further studied.…”

Realizing high color-stability in tetra-chromatic white organic light-emitting diodes by strict manipulation of red emissive layer

“…For instance, in 2016, Zhao et al performed doping of two color phosphors (Blue-Orange) into co-hosts, demonstrated a di-color WOLED with high color stability. 11) However, the color stability is significantly reduced in tri-color WOLED (Blue-Orange-Red) with the addition of red EML, which is due to the strong charge trapping effects of the red dye [Ir(MDQ) 2 (acac)]. In 2019, Dai et al adopted three ultrathin doping-free phosphorescent EMLs of blue, green and orange, to fabricate an all-phosphor WOLED.…”

“…The same phenomenon was also observed in doping system WOLED. 11) In order to verify the presence of hole and electron trapping in the red dye, the Hole-only and Electron-only devices with different thicknesses of Ir(piq) 2 (acac) were 3. In both Electron-only and Holeonly devices, the current density of the device without red dye is larger than that of device with red dye.…”