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Transient electroluminescent measurement system is used to study the inside charge behavior of prepared organic light-emitting diodes (OLEDs) in this article. Two rectangular pulses with a fixed time interval are supplied on the device. We can analyze the inside charge storage and the emitting process by measuring the transient EL and transient current of the device. OLEDs based on the m-MTDATA∶3TPYMB (1∶1) system was prepared. We found that the stable EL intensity increase when the second pulse is supplied. And the increment reduced with the increased current. We also find the electroluminescent under the second pulse decayed faster than that of the first pulse. This is because of the quenching due to the polaron-exciton effect (TPQ) is more serious in the emitting layer under the second pulse.

The accumulation carriers and the trapped carriers are found in many organic light-emitting diodes (OLEDs) more or less, which can lead to a great loss of carriers and weaken the performance of devices. We have investigated a host-guest-system containing the green phosphorescent emitter tris[2-phenylpyridinato-C2,N]iridium(Ⅲ) [Ir(ppy)3] and one host material with transient electroluminescence (EL). The charge recombination, accumulation and light emission mechanisms of the phosphorescent organic light-emitting diodes (PhOLEDs) with different host materials were analyzed. The structure was fabricated as ITO/NPB(30 nm)/host: Ir(ppy)3/BCP(10 nm)/Alq3(20 nm)/LiF(0.7 nm)/Al(100 nm),the hosts were CBP, PVK and TAZ respectively. These results showed the transient EL was strongly dependent on host materials. Compared to devices of host material CBP and PVK, only those with the host material TAZ as the emitting layer exhibited strong electroluminescence overshoots between 1 and 3 μs after turning off the voltage pulse at room temperatures. To further elucidate the generality of the overshoots, we monitored their dependence on the dopant concentration. The transient EL results in host-guest-system devices demonstrated a direct link between the strong overshoot effect and charge trapping in the emitting guest molecules. The excessive electrons in the guest sites could be a major factor inducing significant strong overshoot phenomenon in the TAZ: Ir(ppy)3 layer. We attributed these overshoot effect to the electrons accumulated on Ir(ppy)3 sites and accumulated holes in the vicinity of the HBL/EML interface. As a result, we obtained a better understanding of carriers’ dynamics and recombination process of PhOLEDs after turning off the voltage pules. The new understanding of the charge carriers and exciton dynamics of PhOLEDs is instrumental in directing the efforts of developing stable and high-efficiency PhOLEDs.

The application of fullerenes with two or more adducts as acceptors has greatly enhanced the performance of bulk-heterojunction solar cells with poly (3-hexylthiophene) (P3HT) as the donor. The enhancement is caused by a substantial increase in the open-circuit voltage due to a rise in the fullerene lowest unoccupied molecular orbital (LUMO) level when going from monoadducts to multiadducts. While the increase in the open-circuit voltage is obtained with many different polymers, most polymers other than P3HT show a substantially reduced photocurrent when blended with fullerene multi-adducts such as bis adduct of Phenyl-C61 -butyric acid methyl ester (bis-PCBM) or the indene-C60 bis-adduct (ICBA). Here we investigate the reasons for this change in performance of polymer solar cells(PSCs) based on [6,6]-phenyl C70-butyric acid methyl ester (PC70BM), ICBA and bis-PC70BM as the acceptors and poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b’]dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl]](PTB7)as the donor. The cell configuration is ITO/PEDOT：PSS/active layer /LiF/Al .The PSCs with PC70BM, ICBA and bis-PC70BM show PCEs of 7.29%, 4.92% and 3.33%, respectively. The change of performance of the PSCs could be mainly attributed to the different excition generation and charge collection of PSCs employing different fullerene multi-adducts as acceptors.

TiO2 inverse opals, as well as used as photonic crystals, can be applied to the dye sensitized solar cells (DSSC), photocatalysis, and so on. In above applications, ordering of pore arrangement in TiO2 inverse opal is crucial as it determines the application effect of TiO2 inverse opal. In this paper, TiO2 inverse opals were prepared by infiltrating and removing of polystyrene (PS) colloidal crystal templates. Using scanning electron microscope (SEM), it is found that the pore structure of inverse opals can be tuned by using different heating temperature and different size of PS spheres, and ordering of pore arrangement is strongly affected by ordering of PS spheres alignment, heating temperature, and size of PS spheres.

The considerable performance enhancement of P3HT-based solar cell after thermal annealing can be attributed to the thermodynamically driven partial crystallization and phase segregation of each component. In the present work, thermal annealing was executed by delivering P3HT : PCBM blend films onto the preheated susceptor in a PECVD chamber filled with high purity nitrogen gas. The pressure of inner chamber could be set steadily and precisely in the range of 1 to 1 850 mTorr at 150 °C. It was found that the phase segregation scale of two components was tuned to a certain extent by varying the annealing pressure, whereas the polymer crystallinity was slightly affected. According to the pressure settings, polymer solar cells (PSCs) were fabricated in the following structure: ITO/PEDOT : PSS/P3HT : PCBM/Al. All of the device parameters exhibited the similar trend--an initial increase followed by a decrease, and reached a peak at 1500 mTorr with successive increase in annealing setting pressure. PSC annealed under 1 500 mTorr shows overall high performances with the power conversion efficiency up to 3. 56%. The UV-Vis absorption spectra of annealed blend films shows that the vibronic absorption peaks (shoulders) at 510, 550 and 600 nm became more pronounced under higher setting pressure, which is attributed to better crystalline P3HT with increased π-π stacking of polymer molecules. The AFM results further suggest that high annealing pressure (1000 mTorr) promoted the domain formations of P3HT or PCBM; moreover, a moderate phase segregation, as a result of an appropriate annealing pressure (1500 mTorr), facilitates polymer crystallization which ensures the high charge (hole) mobility and consequently increased short-circuit current and fill factor.

Au was used as anode in some kind of organic electroluminescent devices. Sometimes transparent Au electrodes are required, which means that the thickness of Au electrode should be as thin as possible. Therefore, two metals together forming an electrode become a choice. In the present paper, translucent Au/Al layer was inserted to anode side, and OLED device with the structure of ITO/Al (16 nm)/Au (10 nm)/TPD (30 nm)/AlQ (30 nm)/LiF (0.5 nm)/Al was prepared. There is a spectral narrowing phenomenon on the device ITO/TPD (30 nm)/AlQ (30 nm)/LiF (0. 5 nm)/Al, and through analysis and experiment it was found that this phenomenon comes from selective permeability to light of Au thin film rather than the microcavity effect. The device maintains wide viewing angle, without the angular dependence. And the color purity of device with Au thin film is improved.

Inserting metal thin layer into organic electroluminescent device often brings some unexpected effect. By inserting 5 nm Au thin layer between MoO3 and TPD, we prepared the OLED device with the structure of ITO/MoO3(5 nm)/Au(5 nm)/ TPD/AlQ/LiF/Al. The luminous efficiency is improved as compared to the device without the Au. By analysis, we believe that the Au between MoO3 and TPD formed a small trap for hole to reduce the current density in device. At the same time, since the light transmittance of green light (AlQ) of 5 nm Au is greater than 80%, the brightness of the device was not significantly affected. That is the reasons for the improved luminous efficiency. This work provides some new ideas and experimental evidence for how to improve the luminous efficiency of OLED devices.

In this paper, the blue light properties of LED illumination devices have been investigated. Against the status quo of China's LED lighting, we measured the spectrum component of LED lamps and analyzed the photobiological safety under the current domestic and international standards GB/T 20145-2006/CIE S009/E: 2002 and IEC62471: 2006 standards as well as CTL-0744_2009-laser resolution, which provides the reference to the manufacture of LED lighting lamps as well as related safety standards and laws. If the radiance intensity of blue light in LED is lower than 100 W x m(-2) x Sr(-1), there is no harm to human eyes. LEDs will not cause harm to human eyes under normal use, but we should pay attention to the protection of special populations (children), and make sure that they avoid looking at a light source for a long time. The research has found that the blue-rich lamps can affect the human rule of work and rest, and therefore, the LED lamps with color temperature below 4 000 K and color rendering index of 80 are suitable for indoor use. At the same time, the lamps with different parameters should be selected according to the different distances.

Lighting accounts for approximately 22 percent of the electricity consumed in buildings in the United States, with 40 percent of that amount consumed by inefficient incandescent lamps. This has generated increased interest in the use of white electroluminescent organic light-emitting devices (WOLEDS) as the next generation solid-state lighting source, owing to their potential for significantly improved efficiency over incandescent sources, combined with low-cost, high-throughput manufacturability. The research and application of the devices have witnessed great progress. WOLEDS have incomparable advantages for its special characteristics. This progress report sketched the principle of WOLEDS and provided some common structures, and further investigation of the mechanism of different structures was made. Meanwhile, the key technologies of WOLEDS were summarized. Finally, the latest research progress of WOLEDS was reviewed.

In the present paper, zinc oxide nanorods (ZnO-NRs) were synthesized by the hydrothermal method at lower temperature and the polymer poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) were used to fabricate an electroluminescent device based on the structure of "ITO/ZnO-seed/ZnO-NRs/MEH-PPV/Al". The measurement of current-voltage curve shows that it has a well rectifying characteristic. When a reverse bias exceeding 17 volts was applied to the ZnO-NRs/ MEH-PPV heterojunction, both emissions of ZnO and MEH-PPV were detected. And the intensity of near ultraviolet emission from ZnO is stronger than that of the orange-red emission belonging to MEH-PPV. It was also shown that the light power is gradually promoted with the increase in the reverse bias. Unfortunately, although carriers were injected into the heterojunction under the positive bias, we could not get any emissions. Its mechanism is attributed to the specificity of the organic inorganic hybrid heterojunction and the nanometer effects of ZnO-NRs. It is concluded that tunneling electroluminescence happens in this prepared device under the reverse bias.

Three kinds of porphyrins which can abbreviate as TPP, TPPCu and TMPPFeCl were synthesized by one-step method with mixed solvents. Then these porphyrin materials were used as donors to fabricate organic solar cells with PCBM as accepter by the solution processing of spin-coating method. The structure is ITO/porphyrin : PCBM/Al. The photovoltaic characterizations of these devices were investigated. The device based on TPP : PCBM shows the best performance with an open circuit voltage (V(OC)) of 0.52 V, a short circuit current (J(SC)) of 0.98 mA x cm(-2), and fill factor (FF) of 30.1%. Then the influence of different weight ratio of TPP : PCBM was researched. The best weight ratio of TPP : PCBM is 1 : 1. Increasing or decreasing the quatity of TPP would make J(SC) and V(OC) of the device deterioration and have little effect on the FF.

The present work investigates the photoluminescence (PL) and electroluminescence (EL) characteristics of Eu-complex Eu (UVA)3Phen doped PVK with different doping concentrations. The results indicate that there exists Forster energy transfer from PVK to Eu(UVA)3 phen in the mixed system. It can get good color purity by optimizing the doping concentration of host and guest materials. And the authors can obtain the best doping concentration to be 4% in EL device.

In the present work, the photoluminescence (PL) and electroluminescence (EL) characteristics of Tris[2-(2,4-difluorophenyl)pyridine]iridium(III) (Ir(Fppy)3) doped poly(n-vinylcarbazole) (PVK) with different doping concentrations were investigated. And a blue phosphorescent organic light-emitting diode (OLED) with the structures of ITO/PEDOT : PSS/PVK : Ir(Fppy)3/BCP/Alq3/LiF/Al was fabricated. The experimental results show that the luminescence performances of devices are different as the doping concentration of Ir(Fppy)3 is different. When the doping concentration of Ir(Fppy)3 is lower, the luminescence of PVK can be found in EL spectra. When the doping concentration is too high, concentration quenching may occur. As the doping concentration is suitable, the luminescence of PVK can not be found, only the luminescence of Ir(Fppy)3 can be found in EL spectra. It is concluded that the device with doping concentration of 4% has the best photoelectric performance according to its current density-voltage-luminance curve.

Series of organic light emitting devices with basic structure of ITO/PCBM: PVK(x Wt%, approximately 40 nm)/DPVBi(30 nm)/Alq3 (30 nm)/Al were fabricated in order to investigate the carrier recombination region movement in these devices. The carrier injection-dependent, the carrier transport-dependent and the voltage-dependent carrier recombination region movements were investigated respectively by modifying cathode with lithium fluoride, by changing the doping concentration of PCBM and by changing the voltage on the devices. The physical mechanism behind the voltage-dependent carrier recombination region movement was discussed.

To assess the value of contrast-enhanced ultrasound imaging in monitoring the therapeutic effect of argon-helium cryosurgical treatment of malignant tumors.Before and after argon-helium cryosurgical treatment, 42 patients underwent contrast-enhanced ultrasound imaging, conventional ultrasound imaging and enhanced CT or magnetic resonance imaging (MRI) for examining the number of tumor foci and the size of necrotic areas.A total of 80 tumor lesions were detected by contrast-enhanced ultrasound imaging. Compared with conventional ultrasound imaging, contrast-enhanced ultrasound imaging detected a significantly greater number of tumors and the intratumoral necrotic areas (96 vs 19) as well as a significantly increased mean size of necrotic areas (5.7∓3.6 cm vs 2.8∓1.7 cm), showing no significant differences from the results by enhanced CT and MRI (94 and 5.5∓3.3 cm, P=0.872 and 0.978, respectively). The short-term therapeutic effect of argon-helium cryosurgery evaluated by contrast-enhanced ultrasound imaging were also similar to that assessed by enhanced CT or MRI (P=0.906).Contrast-enhanced ultrasound imaging has important values in monitoring malignant tumors during argon-helium cryosurgical treatment and in evaluating the short-term therapeutic effect of the treatment.

In the present work, in order to improve electron injection and transport at the interface of the hole blocking layer (HBL) and the electron transport layer (ETL) in the hole-domain solution processed phosphorescent organic light emitting devices (PhOLEDs), the mixed interface layer (MIL) was fabricated by partially co-doping hole blocking material 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) and electron transport material tris(8-quinolinolato) aluminum (Alq3) between HBL/ ETL. The MIL thickness was kept at 10nm, while the doping ratio of these two materials varied. Under a given electric field, the devices with the MIL at any mixed ratios all show much higher luminance and current density than those with a typical interface. For example, the luminance power and current density at 10 V for a typical device are 1.03 microW and 5.13 mA x cm(-2), while in case of mixed interface are 3.64 microW and 18.1 mA x cm(-2), respectively. From data results and theoretical analysis, the possible derivation of these improvements is considered to be the reduced electron accumulation at the interface resulting from the reduced electron injection energy barrier and lowered transport mobility by BCP material, which leads to an increase in electron amount in the emission layer and therefore the higher luminance and current density.

The present work investigates the effects of different buffer layers on the performance of blue organic light-emitting diodes (OLEDs), and compares them with the device with no buffer layer. Two kinds of blue OLEDs with 4,4'-bis(2,2'-diphenyl vinyl)-1,1'-biphenyl (DPVBi) as the emitting layer, N, N'-bis-(1-naphthyl)-N, N'-1-diphenyl-1,1 '-biphenyl-4, 4'-diamine (NPB) as the hole transporting layer, and copper phthalocyanine (CuPc) and poly(3,4-ethylenedioxythiophene) : poly (styrenesulphonate) PEDOT : PSS as the hole injection layer respectively were fabricated with the structures of ITO/CuPc/NPB/DPVBi/BCP/Alq3 /Al and ITO/PEDOT : PSS/NPB/DPVBi/BCP/Alq3/Al. Moreover, the effects of different preparation technology of CuPc on the performance of OLEDs were also investigated. It was found that the performance of the devices with a hole injection layer is better than that of the device without any hole-injection layer. Although the luminance and efficiency of the water-soluble CuPc based device are worse than that of the device with thermally evaporated CuPc, but better than that of the device with water-soluble PEDOT : PSS. So the water-soluble CuPc is a good hole injection material because it is easier to fabricate the film than traditional CuPc.

Bulk heterojunction polymer solar cells based on the blend of MEH-PPV (poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene]) and PCBM (1-(3-mehyloxycarbonyl)propyl-phenyl[6,6]C61) were fabricated. The thickness of the active layer was controlled by changing the concentration of MEH-PPV : PCBM (1 : 4 in weight ratio) solution and spin speeds. Investigation of the effects of active layer thicknesses on the performance of the photovoltaic devices indicates that, when the spin-coated speeds are lower than 4,000 r x min(-1) (round per minute), the open-circuit voltage (V(oc)) remains almost unchanged at approximately 0.8 V, whereas the short-circuit density (J(sc)) monotonically increases and the fill factor (FF) decreases slightly. The spin speeds that are higher than 5,000 r x min(-1) rpm result in the V(oc) and J(sc) both reduced. The V(oc) decreases from 0. 78 V at the spin-speed of 5,000 r x min(-1) to 0.67 V at 8,000 r x min(-1), and the J(sc) even decreases from 3.96 mA x cm(-2) at 5 000 r min(-1) to 1.76 mA x cm(-2) at 8,000 r x min(-1). J(sc) depends on the mutual impact of light absorption and carrier transport, while a contradicting effect from the two aspects is caused by varying the thickness of the active layer. The thicker the active layer, the more the excitons induced by light absorption. However, the build-in electric field becomes weaker and the pathway becomes longer for transporting the opposite charge carriers derived from exiciton separation to their corresponding electrodes at the same time, which makes the probability of charges collection by respective electrodes lower. With respect to the reduced V(oc), it may be attributed to the increased proportion of exciton dissociation at the interfaces of MEH-PPV and PCBM with the relevant electrodes.

With the development of organic light-emitting diodes, interests in the mechanisms of charge carrier photo generation, separation, transport and recombination continue to grow. Phosphorescent organic light-emitting diodes have gained considerable interest in the last 10 years because of high luminance efficiency. In the present paper, the authors investigated the optical and electrical characteristics of the devices based on Ir(ppy)3 and Ir(piq)3 doped PVK matrix emission layer at room temperature. The PL spectra show that the energy transfer from PVK to Ir(piq)3 is harder than that of PVK to Ir(ppy)3. The Luminescence characteristics of devices with different doping ratio show that it is not the energy transfer from matrix, but the recombination of injected carriers on phosphorescent molecules that is the main origin of EL emissions. From the viewpoint of energy level, the characteristics of carrier-trap and transport in Ir(piq)3 are better than in Ir(ppy)3 due to the high HOMO and low LUMO in Ir(piq)3.

A deep red emission polymer (PPV-Q) was synthesized successfully. The photoluminescence, electroluminescence and absorption performance of this polymer were studied in detail. The experimental results show that the polymer has strong absorption in the ultraviolet and blue emission wavelength region. The effective excitation wavelength is about 463 nm. The organic emitting diodes based on the polymer as the active layer were prepared with the device structure: ITO/PPV-Q/Al. The electroluminescence of these devices was obtained and the peak emission wavelength is about 670 nm; the electroluminescence spectra have the full width at half maximum of about 90 nm. The CIE coordinate remains constant at (x = 0.67, y = 0.32) without change with the increase in driving voltage. The electroluminescence of this device (ITO/PPV-Q/Al) shows deep red emission. However, the current increases with the increase in driving voltage.

Nanocrystalline ZnS thin films were fabricated by glancing angle deposition (GLAD) technology in an electron beam evaporation system. Deposition was carried out in the custom vacuum chamber at a base pressure 3 x 10(-4) Pa, and the deposition rate was fixed at 0.2 nm x s(-1). ZnS films were deposited on pieces of indium tin oxide (ITO) substrates when the oblique angle of the substrate relative to the incoming molecular flux was set to 0 degrees, 80 degrees and 85 degrees off the substrate normal respectively. X-ray diffraction (XRD) spectra and scanning electron microscope (SEM) images showed that ZnS nanocrystalline films were formed on the substrates at different oblique angle, but the nanocolumn structure was only formed under the situation of alpha = 80 degrees and 85 degrees. The dynamics during the deposition process of the ZnS films at alpha = 0 degrees, 80 degrees and 85 degrees was analyzed. The transmitted spectra of ZnS thin films deposited on ITO substrates showed that the ZnS nanocolumn thin films could enhance the transmissivity in visible range. The ZnS nanocolumn could be used into electroluminescence device, and it would enhance the luminous efficiency of the device.

Three organic devices with different quantum well period were fabricated. The potential barrier layer and well layer for electrons were made of N,N'-diphenyl-N,N'-bis(1-napthyl)-1,1'-biphenyl 1-4,4'-diamine(NPB) and 4,4,N,N'-dicarbazolebiphenyl(CBP). The photoluminescence quenching of these three devices under changed reverse voltages were studied. Results showed that photoluminescence quenching of NPB layer occurs more quickly than that of CBP layer in the authors' devices. This is because that the effective electric field in NPB layer is higher than that in CBP layer. The excitons in NPB and CBP layer were easily to be dissociated when the quantum well period increased under the same reverse voltage. Since these three devices are type II quantum well structure, the excitons in these devices are not very stable.

A novel rare earth complex Eu(TTA) (2NH2-phen)3 was synthesized. The Eu complex was blended with poly(N-vinylcarbazole) (PVK) in different weight ratios and spin coated into films. The photoluminescence of Eu(TTA) (2NH2-phen)3 was obtained. Multilayer devices with PVK : Eu(TTA) (2NH2-phen)3 as the active layer were fabricated, and the device structure was ITO/PVK : Eu(TTA) (2NH2-phen)3 / 2,9-dimethyl-4,-diphenyl-1, 10-phenan throline(BCP) /8-hydroxyquinoline aluminum(Alq3)/Al. The influence of Eu(TTA) (2NH2-phen)3 doping concentration on electroluminescence spectroscopy was studied. It was found that the EL spectra do not change with the doping concentration. The spectral overlapping of the emission spectrum of PVK and the absorption spectrum of Eu(TTA) (2NH2-phen)3 is very small. From the above experimental results, it can be demonstrated that the mainly mechanism of Eu(TTA) (2NH2-phen)3 EL is charge carrier directly trapped by ligand.

The growth mechanism and crystallization phase state were investigated by the methods of atomic force microscopy (AFM) and X-ray diffraction (XRD). The pentacene films were deposited with a self-assembling monolayer by thermal evaporation on p(+)-Si wafer substrates at room temperature and annealed at a constant temperature (80 degrees C) for 120 min. The experimental results show that pentacene films were grown with terraces island structure with the diameter of island of about 100 nm and constituted a layer consisting of faceted grains with a average step height between terraces of 1.54 nm x s(-1), which were accord with the long axis length of pentacene molecule, and the film were vertically grown on the substrate surface. The crystallization of pentacene thin films is shown in XRD pattern. The increase in the thin film thickness introduced a second set of diffraction peaks, which were attributed to the pentacene triclinic bulk phase. The critical thickness of both phases is 150 and 80 nm, respectively. At a film thickness of 150 nm, the triclinic phase diffraction peaks become the dominant phase. This is contrast to the XRD spectrum of very thin film of 80 thickness, where the thin film phase is the only contribution.

Solid state cathodoluminescence is a brand-new excitation mode. In the device, electron acceleration layer plays a very important role in obtaining high energy hot electrons to excite organic luminescent materials in solid state cathodoluminescence. Two kinds of structural devices (A: ITO/MEH-PPV/SiO2/Al, B: ITO/MEH-PPV/ZnO/Al) were fabricated. The theoretical calculation and analysis show that the tunnel current and electric field was higher in SiO2 layer than that in ZnO layer under the same applied driving voltage. The experimental results show that the intensity of device A with SiO2 as electrons acceleration layer is stronger than that of device B with ZnO as electrons acceleration layer under the same driving voltage. And the result demonstrated that electrons in the conduction band of SiO2 can be heated to higher energy than that in ZnO.

It is considered that the efficiency of fluorescent material based organic light emitting diodes can be enhanced by introducing a phosphorescent sensitizer. In the present work, devices with emission layers (EML) of fac-tris(2-phenylpyridinato-N, C2') iridium (III) (Ir(ppy)3)-sensitized-fluorescent materials were fabricated. Ir(ppy)3 was co-doped with DCJTB and rubrene in PVK matrix, respectively. When the doping ratio was proper, pure emission from fluorescent material can be achieved. Furthermore, the sensitizing mechanism and effect were analyzed. A weak effect between Ir(ppy)3 and DCJTB was found. It was deduced that the weaker sensitizing effect is related to the poor film appearance.

The authors fabricated OTFT devices with different insulator materials. The OTFTs with PMMA as the dielectric layer exhibit better properties, including a mobility of 0.207 cm2 x V1 x s(-1), an on/off current ratio of 4.93 x 10(3), and a threshold voltage of 4.3 V. However, the OTFTs based on oxidized silicon dielectric layer perform not so well, with a mobility of 0.039 cm2 x V(-1) x s(-1), an on/off current ratio of 5.98 x 10(2), and a threshold voltage of 5.4 V. In order to explain the difference in performances, we compared the surface roughness of the oxidized silicon film with that of the PMMA film according to the results of atomic force microscopy, and found that the former had a roughness mean square (RMS) of 1.579 nm and the latter was more smooth with an RMS of 0.216 nm. The quality of the pentacene films deposited onto oxidized silicon and PMMA was also studied by atomic force microscopy and X-ray diffraction. From the results of AFM, the authors found that the pentacene film deposited on PMMA had high thin film quality with larger grain size and less crystal grain boundaries. From the results of XRD, the authors found that the pentacene film deposited on PMMA had clear diffraction peak, showing that the pentacene film deposited on PMMA had greater crystallite quality once again. Therefore, OTFTs with PMMA as insulator layers have advantages over those OTFTs with oxidized silicon dielectric layer.

The changes of exciton generation region are influenced by varying electric field, which affect the color and efficiency performance of devices. Firstly, The authors fabricated two types of phosphorescent light emitting devices, device 1:ITO/PEDOT : PSS/PVK : Ir(ppy)s : DCJTB (100:2:1 wt)/BCP(10 nm)/Alq3 (15 nm)/Al, and device 2: ITO/PEDOT : PSS/ PVK : Ir(ppy)3 (100:2 wt)/BCP (10 nm)/Alq3(15 nm)/Al. The authors investigated the influences of electric field on exciton generation region in single-layer and multi-doped structure devices. Analysis of the electroluminescence spectrum under different voltages indicates that the emitting of Ir(ppy)3, PVK and DCJTB was enhanced with the increase in applied voltages. Compared to Ir(ppy)3, the emitting of PVK and DCJTB was prominently enhanced. This is because under high electric field it is easier high energy carrier to generate high energy exciton, and the emitting of wide-band-gap material PVK is stronger; on the other hand, the authors investigated the results from the aspect of energy band gap. DCJTB is narrow-band-gap material, which can capture carrier comparatively easily and emit stronger light. At the same time, we obtained a new emission peak located at 460 nm, which becomes comparatively weak with increasing voltage. In order to explore the reason, we fabricated the device: ITO/ PEDOT: PSS/PVK : BCP : Ir(ppy)3 (x:y:2 wt)/Alq3 (15 nm)/Al. The 460 nm emission peak doesn't disappear by changing the mass ratio of x and y. The authors speculate that the emission peak relates to PVK and BCP.

The devices with phosphorescent material tris(2-phenylpyridine)iridium [Ir(ppy)3] and fluorescent material 5,6,11, 12-tetraphenylnaphthacene [Rubrene] as dopants in two kinds of host were constructed in the present study. Respectively, the two kinds of host are polyvinylcarbazole [PVK] and 4,4'-N,N-dicarbazole-biphenyl [CBP]. We studied the properties of energy transfer between host materials and dopants. Firstly, the absorption and photoluminescence spectra of PVK, CBP, Ir(ppy)3 and Rubrene were measured. The spectral overlap between the photoluminescence of PVK and the absorption spectrum of Ir(ppy)3 is larger than that of Rubrene. The result of the spectral overlap for CBP is the same as PVK. It was shown that the energy transfer from the two host materials to Ir(ppy)3 is stronger than that to Rubrene. In addition, the energy transfer from Ir(ppy)3 to Rubrene is possible according to their absorption and photoluminescence spectra. We compared the electroluminescence properties of different devices. In devicel of ITO/PVK : Rubrene : Ir(ppy)3 (100 : 5 : x)/BCP(10 nm)/Alq3 (20 nm)/Al and device 2 ITO/CBP : Rubrene : Ir(ppy)3 (100 : 5 : x)/BCP(10 nm)/Alq3 (20 nm)/Al(x = 0, 3), under the same DC bias, the electroluminescence results show that energy transfer from host to Rubrene through Ir(ppy)3 is the main mechanism. And energy transfer is much more efficient in CBP as host than in PVK. In addition, at the same voltage, the light power of the device doped with Ir(ppy)3 and Rubrene is obviously stronger than that of the device doped with Rubrene only. When the concentration of Ir(ppy)3 increases, the light power decreases at the same voltage, and the effect of concentration quenching is enhanced.

The radio frequency (r. f.) magnetron sputtering was used for preparing silicon-rich silicon nitride films deposited on polished Si substrates at 80 degrees C substrate temperature. The high-purity Ar was used as a sputtering gas and the high-purity N2 as a reactive gas. The silicon nitride films with different Si-rich degrees were obtained by changing the flow ratio of Ar/N2, and subsequently the samples were annealed at a high temperature in pure N2 ambience. The influence of annealing on the properties of films was investigated by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and photoluminescence (PL). The appearance of Si-N bonds can be confirmed by the XPS, from which the ratio of Si/N can be rough estimated. Therefore, the XPS reveals that the sample before annealing has a high content of Si which is the premise to come into being nanometer Si. However, the PL peak of the films before annealing in the visible light region was not observed obviously. The XRD results indicate that the presence of Si clusters buried in the films after annealing was confirmed by two novel diffraction peaks, which are related to nanometer Si. As the flow ratio of Ar/N2 decreased, the emission intensity of PL peak in the visible light region was enhanced, accompanied with a blue-shift of emission peak. According to the quantum confinement effect, the blue-shift of PL peak should be attributed to the enlarged band gap of Si clusters in the sample, and the increased intensity of the PL peak turns out to be due to the size of nanometer Si. The two important factors of annealing treatment and flow ratio of Ar/N2 were studied, which have an intimate connection with emitting mechanism in PL. The blue-shift of PL peak caused by nanometer Si embodied in the silicon nitride thin films depends on the sputtering condition, such as flow ratio, deposition temperature and sputtering pressure.

The National Museum of Health and Medicine, primary named Armed Medicine Museum, is subordinated to the Armed Forces Institute of Pathology, and is one of the few museums in the United States that collects archives and displays human remains. The museum was founded in 1862 to document the effects of war wounds and disease on the human body, the museum has a long history of collecting and preserving human remains from military and civilian sources. This collection provides a rich source of data for researchers in forensic medicine, anthropology, pathology and military medicine. The specimens comprising the anatomical collections are available for research, exhibition, and other educational purposes. The collections have attracted hundreds of domestic and foreign researchers.

Improving on the sealing and high pressure conditions of traditional hydrothermal method, vertical ZnO nanorod arrays were synthesized on indium tin oxide substrate by employing Zn(NO3)2 x 6H2O, (CH2)4N6 as the starting materials in the presence of polyethylenimine(PEI) at ambient pressure and low temperature (92 degrees). Between the substrate and the nanorods, a layer of ZnO flim was prepared as buffer layer and seed layer. The ZnO film was gained by spin-coating zinc acetate solution on indium tin oxide substrate, then annealed at 350 degrees C for 20 min, which can make zinc acetate decompose into zinc oxide. The zinc acetate spin-coating and decomposition procedure was carried out twice to ensure a complete and uniform coverage of ZnO seeds. The second layer was annealed at 500 degrees C for 30 mini Different spin-coating speeds were adopted, one was 2500 r x min(-1), and the other was 5000 r x min(-1). XRD result indicated that the seed layer with 5000 r x min(-1) has better alignment than the layer with 2500 r x min(-1). The aligned seeds with 5000 r x min(-1) show only a (002) reflection, indicating their complete c-axis texturing, whereas the spin-coated seeds give a powder pattern because they rest at all angles on the substrate. SEM result shows that the layer is made up of grains with an the average size of about 30 nm. Well-aligned ZnO nanorod arrays were synthesized by putting the substrate with ZnO seeds into the precursor solutions vertically for one hour. The nanorod arrays were taken out and rinsed with clean ethanol and pure-water for several times, blown dry with a stream of nitrogen, then annealed at 400 degrees C for 30 min in order to wipe off the organic solvent. At room-temperature, the SEM and XRD were measured. SEM results indicate that the crystal structure of most of ZnO nanorods is hexagonal wurtzite crystallographic phase structure, mainly vertical to the substrate. ZnO nanorods have good crystallization, the diameter of the rods is around 40 nm, and the length is above micrometer. The XRD results showed the nanorod arrays have (002) and (004) angles, and the (002) is quite strong. Absorption spectra of the nanorod arrays shows ZnO essence absorption and strong ultraviolet absorption, indicating that ZnO has good quality. Optical properties were studied, and the excitation spectra of the nonorod arrays showed a strong and narrow peak at 387 nm with FWHM smaller than 30 nm and a weak blue peak.

Solid state cathode luminescence (SSCL) is a bran-new excitation mode. In the device, the inorganic semiconductor is used for electron acceleration. After acceleration the energy of electrons may be raised up so high that these hot electrons have enough energy to induce luminescence in the visible region by impact excitation. It is a new development and application of the traditional CRT theory in solid organic/inorganic electroluminescence device, and it is a new method to improve the EL efficiency. a new phenomenon of co-existence of different mechanisms of excitations in addition to these kinds of excitations. It is very important that all these effects are additive, amplifying or compensatory and reinforce the luminescence intensity and make the spectrum of luminescence wider. The accelerating layer of SSCL is the important part of improving the performance of SSCL devices, in which electrons can be accelerated to hot electrons with high energy and obtain electron multiplication. It is the key to improving the performance of SSCL devices, enhancing injecting electrons to increase hot electrons. So we prepared the complex accelerating layer with SiO2, ZnS and ZnO, giving attention to acceleration and injecting property. Firstly, we respectively prepared the devices with the polymer MEH-PPV and SiO2, and ZnS, and ZnO, and found that SiO2/ZnS and ZnO/SiO2 are better. And then contrasting them, we found SiO2/ZnS is better. It's because that ZnS and ZnO are similar in injecting property, but ZnS is evidently better than ZnO in electron multiplication. SiO2 is the primary accelerating layer, and ZnS can lower the voltage barrier by ladder voltage barrier. Finally, we found that this complex accelerating layer, especially in high electric field, can increase the efficiency of SSCL devices by increasing initial electrons and hot electrons.

Many organic matters including heavy metal ions can validly utilize the singlet and triplet for luminescence owiog to the spin-orbit coupling. As a result, the internal quantum efficiency can easily achieve a value higher than traditional organic light emitting diodes in theory. There is a strong luminescence of PVK in PVK : PBD : Rubrene system. PL spectra excited by 345 nm of PVK : PBD : Rubrene thin film has a 410 nm PVK luminescent peak and a 560 nm Rubrene peak. EL still has a PVK luminescent peak, which should be kept from happening. Excitons can not adequately transferred from the matrix solution to Rubrene. The doping with Ir(ppy)3 improves the PVK : PBD : Rubrene system performance. PL spectra excited by 345 nm of PVK : PBD : Ir(ppy)3 : Rubrene with low concentration of Rubrene has a 510 nm Ir(ppy)3 peak and a new 548 nm one. However, the Ir(ppy)3 peak is smaller and the Rubrene one is bigger in EL spectra. Notably a strong and single luminescence of Rubrene is obtained in EL and PL spectra excited by 345 nm of PVK : PBD : Ir(ppy)3 : Rubrene with high concentration of Rubrene. Meanwhile, the Ir(ppy)3 luminescent peak disappears. The mechanism originates from the phosphorescent effect of Ir (ppy)3. The singlet excitons can basically be transferred from PVK : PBD or Ir(ppy)3 to Rubrene. But most excitons from Ir (ppy)3 can directly tunnel to the fluorescent material and come into being singlet states that can return to ground states and cause luminescence. Rubrene can accept proportional excitons with low concentration. While the concentration of Rubrene is higher, excitons can be entirely accepted by Rubrene. The effect also restricts the luminescent intensity of Ir(ppy)3 and boosts up that of Rubrene. Furthermore, the energy transfer in PVK : PBD : Ir(ppy)3 : Rubrene system is primary the Forester energy transfer. Excitation spectra of Rubrene and emission spectra of Ir(ppy)3 have a large overlap revealing that there is a strong energy transfer and further confirmed the phosphorescent effect of Ir(ppy)3. The doping system with phosphorescence material and small molecules can enhance the brightness and internal quantum efficiency.

The Alq3 and DCJTB were blended with poly (N-vinylcarbazole) (PVK) in different weight ratios and spin coated into films. Multilayer devices with the light emitting layer PVK : Alq3 : DCJTB were fabricated, and their structure was ITO/ PVK : Alq3 : DCJTB/ BCP/Alq3/LiF/Al in which BCP and Alq3 were employed as the hole-blocking and electron-transporting layers respectively, PVK is the blue light-emitting as well as hole-transporting layer. The mass proportion of PVK relative to Alq3 was tuned while the quality ratio of PVK to DCJTB remained (100 : 1). Finally, fairly pure and stabile white emission was achieved when PVK : Alq3 : DCJTB was 100 : 5 : 1. The CIE coordinate was (0.33, 0.36) at 14 V, which is very stable at various biases (10-14 V).

With the increasing development of organic light emitting devices (OLED), interest in the mechanisms of charge carrier photogeneration, separation, transport and recombination continues to grow. Electromodulation of photoluminescence has been used as an efficient probe to investigate the evolution of primary excitation in all electric field. This method can provide useful information on carrier photogeneration, the formation and dissociation of excitons, energy transfer, and exciton recombination in the presence of electric field. The operation of OLED brings electrons and holes from opposite electrodes and generates singlet and triplet excitons. However, triplet excitons are wasted because a radiative transition from triplets is spin-forbidden. Spin statistics predicts that singlet-to-triplet ratio is 1 : 3 in organic semiconductors. One way to harvest light from triplet excitons is to use phosphorescent materials. These materials incorporate a heavy metal atom to mix singlet and triplet states by the strong spin-orbit coupling. As a result, a spin forbidden transition may occur allowing an enhanced triplet emission. Among phosphorescent materials, Ir(ppy)3 has attracted much attention because of its short triplet lifetime to minimize the triplet-triplet annihilation. High quantum efficiencies have been obtained by doping organic molecules and in polymers with Ir(ppy)3. In the present paper, the photoluminescence and electroluminescence spectra of Ir(ppy)3 doped PVK film are measured at room temperature. The device structure is ITO/PEDOT : PSS/PVK Ir(ppy)3/BCP/Alq3/Al. The results show that the luminescence capabilities of devices are different when the concentration of Ir(ppy)3 is different. When the concentration of Ir(ppy)3 is suitable, the luminescence of PVK is lower but that of Ir(ppy)3 is stronger relatively, indicating that the energy transfer from the host materials to the guest materials is sufficient. It is concluded that the device with 5% of Ir(ppy)3 has the best luminescence properties according to its light power-current-voltage curve, meaning that the best concentration of Ir(ppy)3 in such kind of device is 5%.

The effects of PBD on the luminescence properties of PVK : Ir(ppy)3 codoped with PBD with lower concentration were investigated. Two kinds of devices with the structures of ITO/PVK : Ir(ppy)3/PBD/Al and ITO/PVK : Ir(ppy)3 : PBD/ Al were fabricated. PVK emission appears in the electroluminescence (EL) spectra of ITO/PVK : Ir(ppy)3/PBD/Al. The reason is that the Forster energy transfer is not efficient enough in the emission layer, and then the emission layer was doped with PBD. A set of devices were fabricated with the configuration of ITO/PVK : Ir(ppy)3 : PBD/BCP/Al. The doping weight ratio of PVK : Ir(ppy)3 was fixed as 100 : 1, and the weight ratio of PBD changed from 100 : 0 (PVK : PBD) to 100 : 20. The photoluminescence (PL) spectra and electroluminescence (EL) spectra of these devices were measured. Through the analysis of their luminescence, it was found that the brightness of these devices codoped with PBD is improved. The brightness of these devices increases with increasing PBD doping ratio as the ratio does not exceed 100:10 (PVK : PBD). The PBD codoping enhances the injection and transportation of electron, resulting in the enhanced carrier recombination probability. If the doping ratio of PBD exceeds 100 : 10 (PVK : PBD), the brightness of the device decreases. There are two reasons. One is that the superfluous PBD causes the carriers to be imbalanced and induces a larger leakage current. The other is that the superfluous PBD may block the hoping of holes or electrons between the PVK chains. The brightness is the strongest when the weight ratio of PVK to PBD is 100 : 10.

The new complex Tb0.5 Eu0.5 (TTA)3Dipy was synthesized. By doping polymer PVK with Tb0.5 Eu0.5 (TTA)3Dipy, the EL device was fabricated with the structure of ITO/PVK: Tb0.5 Eu0.5 (TTA)3Dipy/PBD/Al using PVK: Tb0.5 Eu0.5 (TTA)3Dipy as the emitting layer. Compared with the blend PVK: Eu(TTA)3, the Tb3+ acts as an energy transfer bridge, which enhances the energy transfer efficiency between PVK and Tb0.5 Eu0.5 (TTA)3Dipy. As a result, the emission of Eu3+ is enhanced with the quenching of the emission of PVK. The process of energy transfer was studied.

By the use of multi-source high-vaccum organic beam deposition system, the authors prepared organic multilayer quantum well structures, which consist of alternate organic small molecule materials PBD and Alq3. Based on 4-period organic quantum wells, different samples with different thickness barriers and wells were prepared. The authors measured the lowest unoccupied molecular orbit (LUMO) and the highest occupied molecular orbit (HOMO) by electrochemistry cyclic voltammetry and optical absorption. From the energy diagrams, it seems like type-I quantum well structures of the inorganic semiconductor, in which PBD is used as a barrier layer and Alq3 as a well layer and emitter. From small angle X-ray diffraction measurements, the results indicate that these structures have high interface quality and uniformity. The photoluminescence characteristics of organic multilayer quantum wells were investigated. The PL peak has a blue-shift with the decrease of the well layer thickness. Meanwhile as the barrier thickness decreases the PL peaks of PBD disappear gradually. And the energy may be effectively transferred from PBD to Alq3, inducing an enhancement of the luminescence of Alq3.

In the present paper, the organic quantum-well device similar to the type-II quantum well of inorganic semiconductor material was prepared by heat evaporation. NPB (N, N'-di-[(1-naphthalenyl)-N, N'-diphenyl]-(1,1'-biphenyl)-4,4'-diamine) and Alq3 (Tris-(8-quinolinolato) aluminum) act as the potential barrier layer and the potential well layer respectively. Besides, the single layer structure of Alq3 was prepared. In the experiments, the Forster nonradiative resonant energy transfer from the barrier layer to the well layer was identified, and the quantum well luminescence device possesses a favorable current-voltage property. The narrowing of spectrum was observed, and the spectrum shifted to blue region continuously when the applied voltage increased.

Solid state cathodoluminescence (SSCL) is a new mechanism of light emission in organic-inorganic system. In the present article, we get SSCL under sinusoidal alternating-current voltage with a structure of ITO/SiO2/MEH-PPV/SiO2/Al. The spectra have two peaks: 410 and 580 nm, which obey molecular theory and band model, respectively. The temporal behaviors of both peaks in SSCL are studied with a new method of estimating lifetime in frequency domain. The intensity of the peak at 410 nm decreases as the frequency of the driving voltage increases, and the intensity of the peak at 580 nm increases as the frequency of the driving voltage increases. The difference in the dependence of light intensity on the frequency of excitation comes from the difference in the lifetime of the two peaks. The lifetime of short wavelength emission is found to be less than 5 ms while that of long wavelength emission is more than 0.05 ms.

A series of YLiF4: Er3+ , Tm3+ , Yb3+ samples were synthesized by hydrothermal method. The concentrations of Er+ and Yb3+ were 1 mol% and 1.5 mol%, respectively. Tm3+ concentration changed from 2 to 8 mol%. The absorption of Er3+, Tm3+ and Yb3+ were observed, and the absorption of Tm3+ increased along with the increase in Tm3+ concentration. The color of upconversion luminescence of YLiF4: Er3+, Tm3+ and Yb3+ excited by 980 nm was white when Tm3+ concentration was low. The blue light resulted from the transition of 1G4--3H6 of Tm3+, the green light from the transition of 4S(3/2)(2H(11/2))--4I(15/2) of Er3+, and the red light from the transitions 1G4--3F4 of Tm3+ and 4F(9/2)--4I(15/2) of Er3+. All the upconversion intensities decreased when Tm3+ concentration increased, but the relative intensity decrease was different due to the interaction between Er3+ and Tm3+.