Efficient fluorescence/phosphorescence white organic light-emitting diodes with ultra high color stability and mild efficiency roll-off

Abstract

Efficient fluorescence/phosphorescence hybrid white organic light-emitting diodes (OLEDs) with single doped co-host structure have been fabricated. Device using 9-Naphthyl-10 -(4-triphenylamine)anthrancene as the fluorescent dopant and Ir(ppy)3 and Ir(2-phq)3 as the green and orange phosphorescent dopants show the luminous efficiency of 12.4% (17.6 lm/W, 27.5 cd/A) at 1000 cd/m2. Most important to note that the efficiency-brightness roll-off of the device was very mild. With the brightness rising up to 5000 and 10 000 cd/m2, the efficiency could be kept at 11.8% (14.0 lm/W, 26.5 cd/A) and 11.0% (11.8 lm/W, 25.0 cd/A). The Commission Internationale de L'Eclairage (CIE) coordinates and color rending index (CRI) were measured to be (0.45, 0.48) and 65, respectively, and remained the same in a large range of brightness (1000–10 000 cd/m2), which is scarce in the reported white OLEDs. The performance of the device at high luminance (5000 and 10 000 cd/m2) was among the best reported results including fluorescence/phosphorescence hybrid and all-phosphorescent white OLEDs. Moreover, the CRI of the white OLED can be improved to 83 by using a yellow-green emitter (Ir(ppy)2bop) in the device.

High-efficiency/CRI/color stability warm white organic light-emitting diodes by incorporating ultrathin phosphorescence layers in a blue fluorescence layer

“…For example, the hybrid WOLEDs with ultrathin red/yellow/green sequence incorporations show ultra-high CRI values of 95-96. Combining a high EQE of 19.34% and color stability, to our knowledge, this is also the first WOLED with good tradeoff among device efficiency, CRI, and color stability [1,13,14,17,18,[21][22][23][24][35][36][37][38][39][40]. Such findings can provide an effective way to achieve low-cost, high-efficiency/ CRI/color stability WOLEDs with unique and simplified …”

“…Furthermore, several interlayers were still required during device fabrication. In fact, the excellent device stability and high CRI for WOLEDs are also key factors that are as important as other parameters, such as high efficiency, high brightness, and low cost [3,8,12,18,25,26]. Although some reported hybrid WOLEDs have realized high efficiency, problems still exist, including poor color stability and low CRI [10,15].…”

“…Towards this end, a series of novel device structures for hybrid WOLEDs have been reported. For hybrid WOLEDs, two types of dominant device architectures have been proposed: the single-emissive layer (single-EML) structure [11,13,[15][16][17][18] and the multi-emissive layer (multi-EML) structure [1,10,11,14,19,20]. In order to obtain ideal white emission in single-EML hybrid WOLEDs, the doping concentration of phosphors in the blue fluorophore host must be precisely controlled.…”

Recent Advances of Exciplex-Based White Organic Light-Emitting Diodes

“…Nowadays, many approaches have been reported to develop high-performance WOLEDs, including managing singlet and triplet excitons for hybrid structures [72][73][74][75], harvesting triplets from blue fluorophors with high T 1 [76][77][78][79][80], having charge-and exciton-confining structures to reduce the efficiency roll-off [81][82][83], combining blue/green/red phosphors with light-outcoupling enhancement techniques [84], adopting color down-conversion media [85], comprising ultrathin emitting layers (EMLs) [86][87][88][89][90], using tandem architectures [91][92][93][94][95], employing excimer systems [96][97][98], eliminating interlayer in hybrid WOLEDs [99,100], and exploiting double multifunctional blue EMLs [101]. Among them, the use of exciplexes in WOLEDs has been actively investigated, since exciplexes can be effectively functioned as (i) fluorescent or TADF emitters; (ii) the hosts of fluorescent, phosphorescent and TADF dopants [102][103][104][105][106][107][108][109][110].…”

Carbazole–Dibenzofuran Dyads as Metal‐Free Single‐Component White‐Color Photoemitters

“…Especially, white‐color OLEDs (WOLEDs) are valuable for practical use of low power consumption lighting devices and backlight of display . At present, WOLEDs are fabricated by mixing or depositing several organic components with different luminescent colors . However, the complicated multistep manufacturing process is required with precise control of the electronic states and mixing ratios of organic components.…”