Highly efficient (EQE 4 27%) Yellow OLEDs using spiro[fluorene-9,9'-phenanthren-10'-one]- carbazole-based donor-acceptor-donor host materials

Four bipolar host materials, with spiro[fluorene-9,9'-phenanthrene-10'-one] acceptors with nitrile fragments and ortho, para-phenyl carbazole, and triphenylamine as donor fragments, namely MS-CN, MS-OC, MS-PC, and MS-TPA, respectively, were designed, synthesized, and their photophysical and electrochemical studies were investigated. All MS-host materials exhibited adequate energy gaps, making them suitable candidates for use as host materials for green, yellow, and red phosphorescent organic light-emitting diodes (OLEDs). We have also designed a series of OLED devices with three different emitting layered architectures to explore their potential in electroluminescence applications. Among the devices using MS-OC, the CN-T2T-blended cohost achieved the highest efficiency among the tested yellow-emitting OLEDs, having a luminance efficiency of 80.0 cd A(-1), power efficiency of 113.0 lm W-1, low turn-on voltage of 2.1 V, high maximum luminance of 142464 cd m(-2), and peak EQE of 27.1%. The maximum efficiency of the device is one of the highest values reported in the literature for PO-01-based devices, demonstrating the high potential of our molecular design for host materials.