Articles you may be interested inInfluence of annealing temperature on electronic and dielectric properties of ZrO2 thin films on Si AIP Conf.Conduction mechanisms and reliability of thermal Ta 2 O 5 -Si structures and the effect of the gate electrode J. Appl. Phys. 97, 094104 (2005); 10.1063/1.1884758Interfaces between 4H-SiC and Si O 2 : Microstructure, nanochemistry, and near-interface traps Metal-oxide-semiconductor capacitors that incorporate ZrO 2 gate dielectrics were fabricated by radio frequency magnetron sputtering. In this work, the essential structures and electrical properties of ZrO 2 thin films were investigated. C-V, energy dispersive x-ray spectrometry, and transmission electron microscopy analyses reveal that an interfacial layer was formed, subsequently reducing the k value of the annealed ZrO 2 thin films. Additionally, the mechanisms of conduction of the Al/ ZrO 2 / p-Si metal/zirconium oxide/semiconductor structure were studied with reference to plots of standard Schottky emission, modified Schottky emission, and Poole-Frenkel emission. According to those results, the dominant mechanisms at high temperatures ͑Ͼ425 K͒ are Poole-Frenkel emission and Schottky emission in low electric fields ͑Ͻ0.6 MV/ cm͒ and high electric fields ͑ Ͼ1 MV/cm͒, respectively. Experimental results indicate that the Al/ ZrO 2 barrier height is 0.92 eV and the extracted trap level is about 1.1 eV from the conduction band of ZrO 2 . The modified Schottky emission can be applied in an electric field to ensure that the electronic mean free path of the insulator is less than its thickness. According to the modified Schottky emission model, the extracted electronic mobility of ZrO 2 thin films is around 13 cm 2 / V s at 475 K. The mean free path of transported electrons in ZrO 2 thin films is between 16.2 and 17.4 nm at high temperatures ͑425-ϳ 475 K͒.
Twon ovel bipolar deep-bluef luorescent emitters, IP-PPI and IP-DPPI, featuring different lengths of the phenyl bridge,w ere designed and synthesized, in which imidazo[1,2-a]pyridine (IP) andp henanthroimidazole (PI) were proposed as an electron acceptor and an electron donor,r espectively.Both of them exhibit outstanding thermal stability and high emission quantumy ields. All the devices based on these two materials showedn egligible efficiency roll-off with increasing current density.I mpressively,n on-doped organic light-emitting diodes (OLEDs) based on IP-PPI and IP-DPPI exhibited externalq uantum efficiencies(EQEs) of 4.85 %a nd 4.74 %w ith CIE coordinates of (0.153, 0.097) and (0.154, 0.114) at 10000cdm À2 ,r espectively.I na ddition, the 40 wt % IP-PPI doped device maintained ah igh EQE of 5.23 %w ith CIE coordinates of (0.154, 0.077) at 10000 cd m À2 .T he doped deviceb ased on 20 wt %I P-DPPIe xhibited ah igher deepblue electroluminescence (EL) performance with am aximum EQE of up to 6.13 %a tC IE of (0.153,0 .078) and maintained an EQE of 5.07 %a t1 0000 cd m À2 .T ot he best of our knowledge,t hese performances are among the state-of-thea rt devices with CIE y 0.08 at ah igh brightness of 10000cdm À2. Furthermore, by doping ar ed phosphorescent dye Ir(MDQ) 2 (MDQ = 2-methyldibenzo[f,h]quinoxaline) into the IP-PPI and IP-DPPI hosts, high-performance red phosphorescentO LEDs with EQEs of 20.8 %a nd 19.1 %w ere achieved, respectively. This work may provide an ew approach for designinghighly efficient deep-blue emitters with negligible roll-off for OLED applications.
To build up efficient host materials, two novel organic small molecules ICz‐PPI and 2ICz‐PPI were designed and synthesized, in which phenanthro[9,10‐d]imidazole (PI) is proposed as a potential luminophore with high stability, while the indolo[3,2,1‐jk]carbazole (ICz) has a high triplet energy and excellent thermal stability. Both exhibited weak intramolecular charge transfer, high decomposition temperature (Td) and high quantum yield. ICz‐PPI and 2ICz‐PPI can act as the emitting layer in non‐doped organic light‐emitting diodes (OLEDs), which achieved an external quantum efficiency (EQE) of 2.47 and 1.94 % with CIE coordinates of (0.153, 0.121) and (0.161, 0.102), respectively. In addition, the high triplet energy allows them to be used as hosts for phosphorescent OLEDs (PhOLEDs). Accordingly, high performance for green (62.5 cd A−1, 70.9 lm W−1, 17.8 %) and red (25.7 cd A−1, 26.9 lm W−1, 19.4 %) had been achieved from the ICz‐PPI‐based PhOLED. Particularly, the ICz‐PPI‐based red PhOLED showed surprisingly low roll‐off and maintained an EQE of 14.9 % at 10 000 cd m−2. Furthermore, an ICz‐PPI‐based white OLED (WOLED) exhibited warm white light (CIEx,y=(0.427, 0.468)) and high efficiencies with a CEmax of 31.8cd A−1, PEmax of 37.0lm W−1 and EQEmax of 14.4 %.
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