Top-contact organic field effect transistors(OFETs) based on poly(3-hexylthiophene)(P3HT) with different concentrations in chloroform(CHCl3) are fabricated.The output characteristics indicate that the P3HT concentration has significant influence on the OFET devices.The performance of the devices firstly is enhanced with increasing the P3HT concentration,and then decreases.The optimized devices with the P3HT concentration of 2 mg/mL show the best performance.The fieldeffect mobility is up to 1.4×10-2 cm2/Vs,the threshold voltage(Vt) is as low as-20 V,and the current on/off ratio(Ion/off) is close to the order of 104.The results suggest that the P3HT aggregation patterns induced by different concentrations can improve the performance of the OFETs.
The driving voltage of an organic light-emitting diode（OLED） is lowered by employing molybdenum trioxide（MoO3）/N,N＇-bis（naphthalene-1-yl）-N,N＇-bis（phe-nyl）-benzidine（NPB） multiple quantum well（MQW） structure in the hole transport layer.For the device with double quantum well（DQW） structure of ITO/[MoO3（2.5 nm）/NPB（20 nm）]2/Alq3（50 nm）/LiF（0.8 nm）/Al（120 nm）],the turn-on voltage is reduced to 2.8 V,which is lowered by 0.4 V compared with that of the control device（without MQW structures）,and the driving voltage is 5.6 V,which is reduced by 1 V compared with that of the control device at the 1000 cd/m2.In this work,the enhancement of the injection and transport ability for holes could reduce the driving voltage for the device with MQW structure,which is attributed not only to the reduced energy barrier between ITO and NPB,but also to the forming charge transfer complex between MoO3 and NPB induced by the interfacial doping effect of MoO3.
We report an effective method to improve the performance of p-type copper phthalocyanine （CuPc） based organic field-effect transistors （OFETs） by employing a thin para-quaterphenyl （p-4p） film and simultane- ously applying V205 to the source/drain regions. The p-4p layer was inserted between the insulating layer and the active layer, and V205 layer was added between CuPc and A1 in the source-drain （S/D） area. As a result, the field- effect saturation mobility and on/off current ratio of the optimized device were improved to 5 × 10-2 cm2/（V.s） and 104, respectively. We believe that because p-4p could induce CuPc to form a highly oriented and continuous film, this resulted in the better injection and transport of the carriers. Moreover, by introducing the V205 electrode＇s modified layers, the height of the carrier injection barrier could be effectively tuned and the contact resistance could be reduced.
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.
Pentacene-based metal-base organic transistors(MBOTs) are fabricated.The influence of the charge carrier injection efficiency at the emitter electrode/emitter interface on the device performance is investigated.It is found that the current modulation and the on/off ratio increase with the injection efficiency.By inserting poly(3,4-ethylenedioxythiophene)(PEDOT):PSS/m-MTDATA layers at the emitter electrode/emitter interface,the current modulation and the on/off ratio reach 6.7 mAcm-2 and 23,respectively.Meanwhile,the current gain is 95-96 in our experiment,which is almost independent on the injection efficiency.
We demonstrate high current efficiency of a blue fluorescent organic light-emitting diode （OLED） by using the charge control layers （CCLs） based on Alq3 . The CCLs that are inserted into the emitting layers （EMLs） could impede the hole injection and facilitate the electron transport, which can improve the carrier balance and further expand the exciton generation region. The maximal current efficiency of the optimal device is 5.89 cd/A at 1.81 mA/cm2 , which is about 2.19 times higher than that of the control device （CD） without the CCL, and the maximal luminance is 19.660 cd/m2 at 12V. The device shows a good color stability though the green light emitting material Alq3 is introduced as the CCL in the EML, but it has a poor lifetime due to the formation of cationic Alq3 species.
