Ca2BO3Cl：Ce3＋, Ca2BO3Cl：Tb3＋, and Ca2BO3Cl：Ce3＋, Tb3＋ phosphors are synthesized by a high temperature solid-state reaction. The emission intensity of Ce3＋ or Tb3＋ in Ca2BO3Cl is influenced by the Ce3＋ or Tb3＋ doping content, and the optimum concentrations of Ce3＋ and Tb3＋ are 0.03 tool and 0.05 mol, respectively. The concentration quenching effect of Ce3＋ or Tb3＋ in Ca2BO3Cl occurs, and the concentration quenching mechanism is d-d interaction for either Ce3＋ or Tb3＋. The Ca21303Cl：Ce3＋, Tb3＋ can produce colour emission from blue to green by properly tuning the relative ratio between Ce3＋ and Tb3＋, and the emission intensity of Tb3＋ in Ca2BO3Cl can be enhanced by the energy transfer from Ce3＋ to Tb3＋. The results indicate that Ca2BO3Cl：Ce3＋, Tb3＋ may be a promising double emission phosphor for UV-based white light emitting diodes.
Bulk heterojunction organic solar cells (OSCs) based on the blend of poly(2-methoxy-5(2′-ethyl-hexyloxy)-1,4-phenylenevinylene (MEH-PPV) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) with different weight ratios (from 1:3 to 1:5) have been fabricated and the effect of annealing treatment on the performance of OSCs has also been studied. Experimental results point to the best optimized doping concentration 1:4 for MEH-PPV:PCBM. Furthermore, it is found that the devices with annealing treatment at 150°C with 8 min show better performance compared with the devices without treatment. The series resistance (R s) is decreased, while the shunt resistance (R sh) increased by nearly 1.5 times. The short-circuit current density (J sc) and fill factor (FF) are improved by annealing treatment. As a result, the power conversion efficiency (PCE) of the devices increases from 0.49 % to 1.21 % with the ratio of 1:3 and from 1.09% to 1.42% with the ratio of 1:4.
SONG JingLuXU ZhengZHANG FuJunZHAO SuLingHU TaoLI JunMingLIU XiaoDongYUE XinWANG YongSheng
In this paper, we report a Schottky ultraviolet photodetector based on poly（3,4-ethylenedioxy-thiophene）poly（styrenesulfonate）（PEDOT：PSS） transparent electrode contacts to Mg0.1Zn0.9O. The I-V characteristic curves of the device are measured in the dark condition and under the illumination of a 340-nm UV light. The device shows a typical rectifying behavior with a current rectification ratio of 103 at ±2 V, which exhibits a good Schottky behavior. The phototo-dark current ratio is high, which is 1×103at-4 V. A peak response of 0.156 A/W at 340 nm is observed. The device also exhibits a wide response from 250 nm to 340 nm, with a response larger than 0.1 A/W. It covers the UV-B region（280 nm-320 nm）, which makes the device very suitable for the detection of UV-B light.
We investigate the amplified spontaneous emission （ASE） from an Ag-backed poly[2-methoxy-5-（2＇-ethylhexyloxy）- 1,4-phenylenevinylene] （MEH-PPV） film with different film thicknesses. The ASE characteristics of Ag-backed MEH- PPV films with different thicknesses show that increasing the film thickness can reduce the influence of the Ag cladding. The threshold, the gain, and the loss of the device with a thickness of 170 nm are comparable to those of a metal-free device. The lasing threshold of this device is about 7.5 times that of a metal-free device. Our findings demonstrate that Ag-backed MEH-PPV film with an appropriate thickness can still be a good polymer gain material for the fabrication of solid-state lasers.
The microstructural, optical, and magnetic properties and room-temperature photoluminescence （PL） ofMn-doped ZnO thin films were studied. The chemical compositions were examined by energy dispersive X-ray spectroscopy （EDS） and the charge state of Mn ions in the ZnO：Mn films was characterized by X-ray photoelectronic spectrometry （XPS）. From the X-ray diffraction （XRD） data of the samples, it can be found that Mn doping does not change the orientation of ZnO thin films. All the films prepared have a wurtzite structure and grow mainly along the c-axis orientation. The grain size and the residual stress were calculated from the XRD results. The optical transmittance of the film decreases with the increase of manganese content in ZnO. The room-temperature photoluminescence of the films shows that the in- tensity of near band energy （NBE） emission depends strongly on the Mn content. The hysteresis behavior indicates that the films with the Mn content below 9at% are ferromagnetic at room temperature.
Li-wei Wang Zheng Xu Fu-junZhang Su-ling Zhao Li-fang Lu
In order to take advantage of organic and inorganic materials,we chose the polymer MEH-PPV as the luminous layer and ZnS as the electron transporting layer to prepare hybrid organic-inorganic light-emitting diodes(HOILEDs):ITO/MEH-PPV(~70 nm)/ZnS(20 nm)/Al by thermal evaporation and spin coating.Compared with the single-layer device ITO/MEH-PPV(~70 nm)/Al,spectral broadening and a slightly red shift are observed.Compared with the pure organic device ITO/MEH-PPV(~70 nm)/BCP(20 nm)/Al and combined with the energy level structure diagram,it is concluded that the spectral broadening and red shift are due to the exciplex luminescence at the interface between MEH-PPV and ZnS or BCP.In addition,the hybrid inorganic-organic device shows a lower turn-on voltage,but the current efficiency is lower than that of the pure organic device with the same structure.
In this work, the influence of a small-molecule material, tris（8-hydroxyquinoline） aluminum （Alq3）, on bulk heterojunction （BHJ） polymer solar cells （PSCs） is investigated in devices based on the blend of poly（2-methoxy-5-（2- ethylhexyloxy）-1,4-phenylenevinylene） （MEH-PPV） and [6,6]-phenyl-C61-butyric acid methyl ester （PCBM）. By doping Alq3 into MEH-PPV：PCBM solution, the number of MEH-PPV excitons can be effectively increased due to the energy transfer from Alq3 to MEH-PPV, which probably induces the increase of photocurrent generated by excitons dissociation. However, the low carrier mobility of Alq3 is detrimental to the efficient charge transport, thereby blocking the charge collection by the respective electrodes. The balance between photon absorption and charge transport in the active layer plays a key role in the performance of PSCs. For the case of 5 wt.% Alq3 doping, the device performance is deteriorated rather than improved as compared with that of the undoped device. On the other hand, we adopt Alq3 as a buffer layer instead of commonly used LiF. All the photovoltaic parameters are improved, yielding an 80% increase in power conversion efficiency （PCE） at the optimum thickness （1 nm） as compared with that of the device without any buffer layer. Even for the 5 wt.% Alq3 doped device, the PCE has a slight enhancement compared with that of the standard device after modification with 1 nm （or 2 nm） thermally evaporated Alq3. The performance deterioration of Alq3-doped devices can be explained by the low solubility of Alq3, which probably deteriorates the bicontinuous D-A network morphology; while the performance improvement of the devices with Alq3 as a buffer layer is attributed to the increased light harvesting, as well as blocking the hole leakage from MEH-PPV to the aluminum （Al） electrode due to the lower highest occupied molecular orbital （HOMO） level of Alq3 compared with that of MEH-PPV.
