Adjusting Performances And Spectra Of The Inverted Polymer Light Emitting Diodes And The Tandem Devices

Although all of the existing OLED products are almost made by organic molecular based vacuum evaporate technology,which still have the disadvantage of huge equipment investment,material waste,low yield and difficult to evaporate large area film.The polymer light emitting diodes?PLEDs?based on the solution processed with the advantage of low cost and easy to acquire large area film gain huge attentions.However,the lifetime of PLED became the bottleneck of its continuous development,the aging of materials resulted by water and oxygen is a key factor for decreasing the lifetime of PLED.Inverted PLED?IPLED?applied metallic oxide as electron transport and hole transport layer,the light-emitting layer is between the two metallic oxide,which can isolate water and oxygen efficiently.In this paper,the reaserch area were centered on the adjusting performances and spectra of the IPLEDs.1.The IPLEDs based on the PF-FSO10 with the structure of ITO/ZnO/PEIE/PF-FSO10?100-700 nm?/MoO₃/Al were fabricated.Due to the macrocavity effects,the device efficiency and EL spectra will have a stronger dependence on the thickness of emissive layer in IPLED.Therefore,we got a series of spectra variation from sky bule to deep blue by adjusting the thickness of emissive layer.A deep blue light?0.15,0.09?IPLED with LE_max of 2.54 cd A^-1 and EQE_max of 3.83%was acquired when the thickness was around 158 nm.The IPLED can get a blue light with LE_max of 5.70 cd A^-1 when the thickness reached to the unimaginable thickness of 700 nm.On the contrary,the conventional device with structure of ITO/PEDOT:PSS/PF-FSO10?100-330 nm?/CsF/Al didn't show the similar phenomenon that should have significant relationship with the distance between metal electrode and recombination area.The IPLED based on normal red fluorescent material PPF-FSO25-DHTBT10 and MEH-PPV,got a near-infrared emission with main peak located at 700 nm and 704 nm,and EQE_max of 0.54%and1.17%,respectively,which create a new route for obtaining near-infrared emission.The variation of emissive layer thickness caused to the changed of recombination area,which led to the widely controlling of EL spectra in IPLED.2.Film morphology and interface controlling were used to balance the transporting of hole and electron charge carrier.When the PF-FSO10 was annealed around its transition temperature?155°C?,the hole mobility decreased due to the inductived hole trap of annealing,on the contrary,the more regular polymer chain led to the increasement of electron mobility.Besides,the process of annealing can also improve the PLQY and the buck density of film,the latter will increase the stability of device.The inserting TPBI layer can benefit to the electron transport,hole and exciton blocking,which can further enhance the device efficiencies.And the optimized IPLED showed an ultimate LE of 6.83 cd A^-1 and an EQE of 7.1%,with CIE?0.15,0.15?.3.High-efficiency solution processed tandem PLEDs,with device structure of ITO/Zn O/PEIE/P-PPV/PEDOT:PSS/PTPA-P/ZnO/PFN-OX/P-PPV/MoO₃/Alwere successfully fabricated by using PTPA-P with HOMO level of-5.0 eV as the electron donor of CGL.After oxygen plasma treating,the surface of the emissive layer changed from hydrophobicity to hydrophily,which offered a possibility for processing water soluble material on the surface of hydrophobicity organic layer.The excellent transmittivity of connecting layer?PEDOT:PSS/PTPA-P/ZnO/PFN-OX?insure the extraction of light.The PTPA-P/ZnO CGL has a more effective charge generation ability than PEDOT:PSS/ZnO CGL,due to the shallower HOMO level of PTAP-P and larger contact area between PTPA-P and ZnO,compared with those based on PEDOT:PSS.The tandem PLED based PTPA-P as electron donor got a LE_max of 26.89 cd A^-1.4.We report on the systematic evaluation of 13 different materials for the cathode and anode in a common LEC configuration.We find that while seven of the materials?Ca,Mn,Ag,Al,Cu,ITO,Au?are suitable for LEC cathode,ITO and Ni are suitable for LEC anode.ITO is the obvious choice for the transparent electrode,while the seven metals are a good fit for the reflective electrode,although it should be noted that Mn is a modest overall reflector and that Cu and Au feature a wavelength-dependent reflection that can render a shifted EL spectrum.We establish that a good electrode performance is directly dependent on that the electrode is both electrochemically inert and capable of doping of the organic semiconductor in the active material at a low overpotential.We also observe that the highest luminance and efficiency is obtained from devices with a balanced height for the cathodic and anodic injection barriers.