ABSTRACT
It has been challenging to develop deep blue organic molecular fluorescent emitters with CIE y (yâ¯≤â¯0.08) based on triplet-triplet annihilation (TTA). Here, we report facilely available dianthracenylphenylene-based emitters, which have a 3,5-di(4-t-butylphenyl)phenyl moiety at the one end and 4-cyanophenyl or 3-pyridyl at the other end, respectively. Both fluorophores show a high glass transition temperature of over 220⯰C with a thermal decomposition temperature of over 430⯰C at an initial weight loss of 1%. The preliminary characterizations of the organic light-emitting diodes (OLEDs) that utilized these nondoped emitters provided high EQEs of 4.6%-5.9% with CIE coordinates (0.15, 0.07-0.08). The analysis of the EL transient decay revealed that TTA contributed to the observed performance. The results show that the new emitters are attractive as a potential TTA-based host to afford stable deep blue fluorescent OLEDs.
ABSTRACT
Organic light-emitting diodes (OLEDs) are driven by injected charges from an anode and a cathode. The low and high work function metals are necessary for the effective injection of electrons and holes, respectively. Here, we introduce a fully novel design concept using organic semiconductor heterojunctions (OSHJs) as the charge injectors for achieving highly efficient OLEDs, regardless of the work functions of the electrodes. In contrast to traditional injected charges from the electrodes, the injected charges originate from the OSHJs. The device performance was shown to be significantly improved in efficiency and stability compared to conventional OLEDs. Attractively, the OLEDs based on OSHJs as charge injectors still exhibited an impressive performance when the low work function Al was replaced by air- and chemistry-stable high work function metals, such as Au, Ag, and Cu, as the cathode contact, which has been suggested to be difficult in conventional OLEDs. This concept challenges the conventional design approach for the injection of charges and allows for the realization of practical applications of OLEDs with respect to high efficiency, selectable electrodes, and a long lifetime.
ABSTRACT
In this Letter, we report the improved light outcoupling efficiency of conventional white organic light-emitting devices (OLEDs) by a kind of multifunctional film with both antireflective and superhydrophobic ability. This film consisted of regular polydimethylsiloxane (PDMS) nanopillar arrays, which were readily batch produced by low-cost imprint lithography. The nanopillar arrays could effectively eliminate the light total reflection and enhance the device efficiency of OLEDs by producing the gradual refractive index due to the decreasing material density from glass to air. Moreover, owing to its superhydrophobicity (contact angle â¼151°), the antireflective film exhibited self-cleaning ability, which was beneficial for keeping the OLEDs substrate clean and ensure the high efficiency of OLEDs. This method is simple, cost-effective, and reproducible. The OLEDs showed an efficiency enhancement of 25% with the multifunctional film.
ABSTRACT
We demonstrate the first white light-emitting device originating from single carbon dot components. A maximum external quantum efficiency of 0.083% at a current density of 5 mA cm(-2) with a color-rendering index of 82 is realized, indicating that carbon dots have great potential to be an alternative phosphor for fabricating white light electroluminescent devices.
ABSTRACT
Asymmetrically 4,7-disubstituted benzothiadiazole derivatives involving a carbazolyl moiety at one end and a solubilizing dendron at the opposite end have been synthesized and characterized. A two-layer electroluminescent device based on one of these solution-processed molecular emitters revealed a maximal luminous efficiency of approximately 10.6 cd A(-1) and green light emission with CIE coordinates (0.34, 0.58).