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 mol 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 Ca2BO3Cl: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℃ with 8 min show better performance compared with the devices without treatment.The series resistance(Rs) is decreased,while the shunt resistance(Rsh) increased by nearly 1.5 times.The short-circuit current density(Jsc) 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 MEHPPV 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.
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 (Alq 3),on bulk het-erojunction (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-C 61-butyric acid methyl ester (PCBM).By dop-ing Alq 3 into MEH-PPV:PCBM solution,the number of MEH-PPV excitons can be effectively increased due to the energy transfer from Alq 3 to MEH-PPV,which probably induces the increase of photocurrent generated by excitons dissociation.However,the low carrier mobility of Alq 3 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.% Alq 3 doping,the device performance is deteriorated rather than improved as compared with that of the undoped device.On the other hand,we adopt Alq 3 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.% Alq 3 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 Alq 3.The performance deterioration of Alq 3-doped devices can be explained by the low solubility of Alq 3,which probably deteriorates the bicontinuous D-A network morphology;while the performance improvement of the devices with Alq 3 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 Alq 3 compared with that of MEH-PPV.
