No abstract

along with a wide T 1 level, especially for blue phosphorescent OLEDs. [7,8] Recently, exciplex formed by an acceptor and a donor is seen as a promi sing candidate for using as a host in OLEDs because of its plastic transport capability and energy band gap. [9][10][11][12][13][14][15] Moreover, most exciplex systems exhibit thermally activated delayed fluorescence (TADF) process via reverse intersystem crossing (RISC), in which triplet excitons can be upconverted into singlet excitons arisen from their minor singlettriplet energy differences (ΔE ST ). [16][17][18][19] It is found that an efficient TADF host could facili tate the energy transfer mechanism vari ation from the Dexter energy transfer to the Förster energy transfer, giving rise to further enhanced device efficiency. [20][21][22] These advantages encourage the devel opment of the exciplex cohost so that many exciplex cohost systems have been reported to demonstrate highly efficient monochrome and white phosphorescent OLEDs. Chang et al. adopted exciplex cohost to realize red, green, blue phosphores cent OLED provided maximum external quantum efficiencies (EQEs) of 8.8%, 14.1%, and 15.8%. [23] Ma et al. demonstrated blue phosphorescent with efficiency of 47.1 lm W −1 as well as white OLED (WOLED) with high efficiency of 75.3 lm W −1 . [24] However, inferior color qualities and instability of spectra are frequently accompanied in these devices. Highly effective exci plex cohost system that is able to realize good colorpure OLED and superior colorstable WOLED has not been reported yet.In this work, a novel exciplex cohost system constructed by the donor of (N,N′dicarbazolyl3,5benzene) (MCP) and the acceptor of 4,6bis[3,5(dipyrid3yl)phenyl]2phenylpyrimi dine (B4PyPPM) was proposed to fabricate phosphorescent OLEDs with simplified structure. Compared with traditional hostsbased devices, the blue/green/orange/red phosphores cent OLEDs based on the exciplex cohost exhibited stable color purity and higher EQEs of 20.1%, 26.3%, 24.6%, 19.8%, respec tively. By combining with blue and orange phosphor, double emission layer WOLED was realized with maximum efficiency of 73.6 lm W −1 and suppressed efficiency rolloff. Furthermore, extremely minor Commission Internationale de L, Eclairage (CIE) coordinates variation was only (0.008, 0.002) over a large luminance range, which was among the best in exciplex co host WOLEDs. Detail investigation demonstrated the balanced charge transport property of exciplex cohost and multipleThe exciplex co-host system is one of the most promising candidates for developing phosphorescent organic light-emitting diodes (OLEDs) with high performance. However, highly effective exciplex co-host system that is able to realize color-pure monochrome OLED and superior color-stable white OLED simultaneously is rarely reported so far. Herein, a novel exciplex cohost system formed by the donor of (N,N′-dicarbazolyl-3,5-benzene) (MCP) and the acceptor of 4,6-bis[3,5-(dipyrid-3-yl)-phenyl]-2-phenylpyrimidine (B4PyPPM) is constructed successfully to ...

In this work, Au nanoparticle-loaded ZnO/ZnFe2O4 (Au-ZnO/ZnFe2O4) microspheres were prepared using a combination of a two-step hydrothermal process and co-precipitation method. The SEM and TEM analyses showed that the synthesized...