Zisheng Su

Highly efficient and color-tuning electrophosphorescent devices based on CuI complex

Highly efficient electrophosphorescence from organic light-emitting devices based on a CuI complex, [Cu(DPEphos)(Dicnq)]BF4 (DPEphos=bis[2-(diphenylphosphino)phenyl]ether and Dicnq=6,7-Dicyanodipyrido[2,2-d:2′,3′-f] quinoxaline), doped into 4,4′-N,N′-dicarbazole-biphenyl is demonstrated. The performances of these devices fabricated by vacuum vapor deposition technique are among the best reported for devices incorporating CuI complexes as emitters. A low turn-on voltage of 4V, a maximum current efficiency up to 11.3cd∕A, and a peak brightness of 2322cd∕m2 were achieved, respectively. The phosphorescent operating mechanism of organic light-emitting devices based on CuI complex was discussed. Electroluminescent colors can be tuned ranging from green-yellow to orange-red region, and its band tail at longer wavelength can cover near infrared.

High response deep ultraviolet organic photodetector with spectrum peak focused on 280 nm

A high response organic deep ultraviolet (DUV) photodetector (PD) with 280 nm as the response spectrum peak was demonstrated. A maximum photoresponse of 309 mA/W under 280 nm UV illumination with an intensity of 0.428 mW/cm2 and a detectivity of 1×1012 cmHz1/2/W at −8 V were achieved, respectively. The optimized PD diode has a structure of ITO/m-MTDATA (10 nm)/m-MTDATA:Bphen(1:1, 60 nm)/Bphen (10 nm)/Cs2CO3: Bphen (30 wt %,10 nm)/Al(12 nm)/TPD(40 nm). Under 280 nm constant and shuttered illumination conditions with an intensity of 0.18 mW/cm2 the operational time is longer than 440 min when its response respectively decreases to 50% and 83% of its original value. The realization of the DUV detection is attributed to the stronger absorption of shorter UV wavelengths of Bphen acceptor and covering UV waveband longer than 300 nm by the TPD layer. The more detailed mechanism of harvesting the high PD performance is also discussed.

Hydrothermal Syntheses of Some Derivatives of Tetraazatriphenylene

Abstract Some derivatives of tetraazatriphenylene can be synthesized readily by a hydrothermal synthetic method. Compared with the traditional technique, this method is effective and simple process, and much high yields of products with higher purity can be harvested.

High response organic ultraviolet photodetector based on blend of 4,4 ', 4 ''-tri-(2-methylphenyl phenylamino) triphenylaine and tris-(8-hydroxyquinoline) gallium

The authors demonstrate high response organic ultraviolet (UV) photodetector (PD) using 4,4′,4″-tri-(2-methylphenyl phenylamino) triphenylaine (m-MTDATA) and tris-(8-hydroxyquinoline) gallium (Gaq3) to act as the electron donor and acceptor, respectively. The m-MTDATA:Gaq3 blend device shows a photocurrent of 405μA∕cm−2 at −8V, corresponding to a response of 338mA∕W under an illumination of 365nm UV light with an intensity of 1.2mW∕cm2. The high response is attributed to the enhanced dissociation of geminate hole-electron pairs in the distributed heterojunction of the blend and suppression of radiative decay. Photophysics of the PD involved is also discussed in terms of the performance and device structures.

Highly efficient red OLEDs using DCJTB as the dopant and delayed fluorescent exciplex as the host

In this manuscript, we demonstrated a highly efficient DCJTB emission with delayed fluorescent exciplex TCTA:3P-T2T as the host. For the 1.0% DCJTB doped concentration, a maximum luminance, current efficiency, power efficiency and EQE of 22,767 cd m−2, 22.7 cd A−1, 21.5 lm W−1 and 10.15% were achieved, respectively. The device performance is the best compared to either red OLEDs with traditional fluorescent emitter or traditional red phosphor of Ir(piq)3 doped into CBP host. The extraction of so high efficiency can be explained as the efficient triplet excitons up-conversion of TCTA:3P-T2T and the energy transfer from exciplex host singlet state to DCJTB singlet state.

Surface plasmon enhanced organic solar cells with a MoO3 buffer layer

High-efficiency surface plasmon enhanced 1,1-bis-(4-bis(4-methyl-phenyl)-amino-phenyl)-cyclohexane:C70 small molecular bulk heterojunction organic solar cells with a MoO3 anode buffer layer have been demonstrated. The optimized device based on thermal evaporated Ag nanoparticles (NPs) shows a power conversion efficiency of 5.42%, which is 17% higher than the reference device. The improvement is attributed to both the enhanced conductivity and increased absorption due to the near-field enhancement of the localized surface plasmon resonance of Ag NPs.

Simple structured hybrid WOLEDs based on incomplete energy transfer mechanism: from blue exciplex to orange dopant.

Exciplex is well known as a charge transfer state formed between electron-donating and electron-accepting molecules. However, exciplex based organic light emitting diodes (OLED) often performed low efficiencies relative to pure phosphorescent OLED and could hardly be used to construct white OLED (WOLED). In this work, a new mechanism is developed to realize efficient WOLED with extremely simple structure by redistributing the energy of triplet exciplex to both singlet exciplex and the orange dopant. The micro process of energy transfer could be directly examined by detailed photoluminescence decay measurement and time resolved photoluminescence analysis. This strategy overcomes the low reverse intersystem crossing efficiency of blue exciplex and complicated device structure of traditional WOLED, enables us to achieve efficient hybrid WOLEDs. Based on this mechanism, we have successfully constructed both exciplex-fluorescence and exciplex-phosphorescence hybrid WOLEDs with remarkable efficiencies.

High performance small molecule photodetector with broad spectral response range from 200 to 900 nm

We demonstrate a photodetector (PD) with broad spectral response by taking the advantages of more flexible device design in using small molecule materials. The optimized device shows an external quantum efficiency of over 20% from 200 to 900 nm. The high performance is achieved by jointing two donor (D)/acceptor (A) hetero-junctions [m-MTDATA(D)/TiOPc(A) and TiOPc(D)/F16CuPc: PTCDI-C8(A)] such that photoresponses over the deep-ultraviolet (UV) and visible-near infrared regions can be independently optimized. By choosing D- and A-materials with matched energy level alignment, high carrier mobility, and balanced carrier transporting properties, the present PD shows a fast response of 56 ns. The high speed and deep-UV sensitivity might lead to potential military applications such as missile tracking in addition to optical communications, chemical/biological sensing etc.

Very high-efficiency organic light-emitting diodes based on cyclometallated rhenium (I) complex

A phosphorescent (Ph) cyclometallated rhenium (I) (ReI) complex was synthesized by reacting 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline with pentacarbonylbromorhenium in refluxing toluene solutions. The precipitates were easily sublimed to obtain a pure electrically neutral carbonyl diamine ReI complex, (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline)Re(CO)3Br. The Re complex was used as an orange emitting dopant in 4,4′-N,N′-dicarbazole-biphenyl host to fabricate Ph organic light-emitting diodes (PhOLEDs). The maximum electroluminescence (EL) efficiency and luminance of 21.8cd∕A and 8315cd∕cm2 were harvested, respectively, which were the highest EL results among the PhOLEDs based on ReI complexes. The improvements of the EL performances could be ascribed to the synergistic effects of together incorporation of two reciprocally repulsive phenyl and methyl groups on the backbone of 1,10-phenanthroline molecule of the ligand.

Double wavelength ultraviolet light sensitive organic photodetector

The authors demonstrate an organic ultraviolet (UV) photodetector (PD) device in which 1,3,5-tris(3-methylphenyl-phenylamino)-triphenyamine and 1,3,5-tris(N-phenylbenzimidazol-2-yl)-benzene were used as the electron donor and acceptor, respectively. The PD diode offers responses of 75.2 and 22.5 mA/W as the 365 and 330 nm UV light with 1.0 mW/cm2 intensities illuminate the PD diode through anode and cathode sides, respectively. It is interesting that only the planar heterojunction structure diode can provide the special response feature while bulk-heterojunction device could not do it. The working mechanism of the PD diode was also discussed in detail.