We fabricate a kind of novel efficient blue fluorescent organic light emitting device(OLED) based on p-n heterojunctions composed of hole transporting layer(HTL) N,N '-bis(naphthalen-1-yl)-N,N '-bis(phenyl)-benzidine(NPB) and electron transporting layer(ETL) 4,7-diphnenyl-1,10-phenanthroline(BPhen),into which a new blue material,DNCA(a derivation of N 6,N 6,N 12,N 12-tetrap-tolylchrysene-6,12-diamine),is partially doped simultaneously,and double emitting layers are configured.With a turn-on voltage of 2.6 V at 1 cd/m 2,this type of OLED presents a maximum luminance efficiency(η max) of 8.83 cd/A at 5.818 mA/cm 2 and a maximum luminance of over 40000 cd/m 2.Meanwhile,the Commission Internationale De L'Eclairage(CIE) coordinates of this device change slightly from(0.13,0.27) to(0.13,0.23) as the driving voltage increases from 3 V to 11 V.This improvement in the electroluminescent characteristics is attributed mainly to the ideal p-n heterojunction which can confine and distribute excitons evenly on two sides of the heterojunction interface so as to improve the carrier combination rate and expand the light-emitting region.
We report the plasmon-enhanced polymer bulk-heterojunction solar cells with Ag nanoparticles (AgNPs) obtained via chemical method. Here, the AgNPs films with different particle densities are introduced between the poly (3,4-ethylene dioxythiophene) poly (styrenesulfonate) (PEDOT: PSS) buffer layer and the poly (3-hexythiophene):[6,6]-phenyl-c61 butyric acid methyl ester (P3HT: PCBM) layer. By improving the optical absorption of the active layer owing to the localized surface plasmons, the power conversion efficiency of the solar cells is increased compared with the control device. It is shown that the efficiency of the device increases with the density of AgNPs. For the device employing higher density, the resulted power conversion efficiency is found to increase from 2.89% to 3.38%, enhanced by 16.96%.
The metal-conducting single-walled carbon nanotubes(m-SWNTs)with small diameters(0.7 nm-1.1 nm)are selectively removed from the single-walled carbon nanotubes(SWNTs)by using HNO 3 /H 2 SO 4 mixed solution.Semiconducting single-walled carbon nanotubes(s-SWNTs)can be separated efficiently from the SWNTs with high controllability and purity based on this novel method,and the outcome is characterized by Raman spectrum.Moreover,the organic field effect transistors(OFETs)are fabricated based on the poly(3-hexylthiophene-2,5-diyl)(P3HT),and untreated SWNTs and separated SWNTs(s-SWNTs)are mixed with P3HT,respectively.It could be found that the P3HT/s-SWNT device exhibits a better field effect characteristic compared with the P3HT device.The current on/off ratio is increased by 4 times,the threshold voltage is also increased from-28 V to-22 V,and the mobility is increased from 3×10-3 cm2/Vs to 5×10-3 cm2/Vs.
The efficiency of organic light-emitting devices (OLEDs) based on N,N'-bis(1-naphthyl)-N,N'-diphenyl-N,1'- biphenyl-4,4'-diamine (NPB) (the hole transport layer) and tris(8-hydroxyquinoline) aluminum (Alq 3 ) (both emission and electron transport layers) is improved remarkably by inserting a LiF interlayer into the hole transport layer. This thin LiF interlayer can effectively influence electrical performance and significantly improve the current efficiency of the device. A device with an optimum LiF layer thickness at the optimum position in NPB exhibits a maximum current efficiency of 5.96 cd/A at 215.79 mA/cm 2 , which is about 86% higher than that of an ordinary device (without a LiF interlayer, 3.2 cd/A). An explanation can be put forward that LiF in the NPB layer can block holes and balance the recombination of holes and electrons. The results may provide some valuable references for improving OLED current efficiency.
Improved power conversion efficiency(PCE)and stability of organic bulk heterojunction(BHJ)solar cells based on poly(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene)(MEH-PPV)and methanofullerene[6,6]-phenyl C_(61)-butyric acid methyl ester(PCBM)blends are obtained by using ditert butyl peroxide(DTBP)as an additive.The effect of the DTBP contents on the performance of photovoltaic cells is investigated.The results reveal that efficiency enhancement of MEH-PPV:PCBM solar cells can be realized by carefully tuning the contents of DTBP.Compared to the control device,the optimized device with 0.5wt%DTBP additive exhibits enhanced performance with Jsc of(3.51±0.21)mA/cm^(2),FF of(44.45±0.71)%,and PCE of(1.31±0.08)%,increased by 9.3%,8.0%and 22.4%,respectively.The stability of the device is found to be improved by adding 0.5wt%of DTBP.
We have fabricated an organic photocoupler with organic light-emitting diodes(OLEDs) with 520 nm emissive wavelength as the input light source and a photodiode(PD) based on poly(3-hexylthiophene)(P3HT):1-(3-methoxycarbonyl)propyl-1-phenyl-(6,6)-C61(PCBM) as the detector.The influences of buffer layer(PEDOT:PSS) on output current(Iout),current transfer ratio(CTR) and time response characteristics of the photocoupler device were studied.Through our experiments,It is found that the output current linearly increases with the input current,the max output current and CTR of the devices with PEDOT:PSS buffer layer are 2 times and 7 times than that of the devices without buffer layer respectively,which show that the existence of buffer layer can enhance the output photocurrent efficiently.Moreover,the existence of PEDOT:PSS eliminates the time delay of the devices.
In this study the performance of organic light-emitting diodes(OLEDs) are enhanced significantly,which is based on dual electron transporting layers(Bphen/CuPc).By adjusting the thicknesses of Bphen and CuPc,the maximal luminescence,the maximal current efficiency,and the maximal power efficiency of the device reach 17570 cd/m2 at 11 V,and 5.39 cd/A and 3.39 lm/W at 3.37 mA/cm2 respectively,which are enhanced approximately by 33.4%,39.3%,and 68.9%,respectively,compared with those of the device using Bphen only for an electron transporting layer.These results may provide some valuable references for improving the electron injection and the transportation of OLED.
The effect of a new interfacial buffer layer material,rhenium oxide(ReO3),on the performance of polymer solar cells based on regioregular poly(3-hexylthiophene)(P3HT) and methanofullerene [6,6]-phenyl C61-butyric acid methyl ester(PCBM) blend is investigated.The effect of the thickness of the oxide layer on electrical characteristics of the device is also studied.Compared with traditional devices,by inserting a 10 nm-thick ReO3 as the anode buffer layer,a power conversion efficiency(PCE) of 2.8 %(a 37% improvement compared with the control devices) can be obtained with Jsc of 13.6 mA/cm2,Voc of 0.45 V,and a fill factor(FF) of 53.6% under the simulated AM1.5 G 100 mW/cm2 illumination in air.It is indicated that ReO3 can be used as an effective buffer layer to enhance the polymer bulk heterojunction(BHJ) photovoltaic cell efficiency.
