| Since the development of organic semiconductor materials and thin film optoelectronic, there have been much more attention on organic optoelectronics from academic research and application. Especially for rganic light-emitting device (OLED) and organic solar cell (OSC), significant achievements have been achieved in the past two decades. Compared with their inorganic competitors, there are some excellent properties of organic optoelectronics, such as low cost, easy processing, flexible, abundant materials and so on. However, performances of organic optoelectronics is still inferior to inorganic optoelectronics, due to the low intrinsic carrier concentration and mobility of organic semiconductors , the unmatched energy level of electrode interface of organic devices. Therefore, optimization of the carrier injection and transporting is important for improving the performances of organic optoelectronics. In this thesis, we enhance carrier injection and transporting of devices by the methods of doping with inorganic complex in carrier transporting layer, designing suitable device configurations, and developing novel transparent conducting anode. The research achievements and innovations of this thesis are as followings:1. Enhanced performance of OLED by dual doping of LiF in electron transporting layer (ETL) and hole transporting layer (HTL). Different from early study using LiF as the cathode buffer layer or n-type dopant in OLEDs, we propose LiF as dopant materials both for ETL and HTL. The results indicates that LiF doped ETL could effectively enhance the electron injection and transporting. Although LiF doped HTL could decrease hole injection, the hole transporting ability could been improved by LiF doped in HTL. The device performance could be dramatic improved by LiF dual doped in HTL and ETL with the suitable doping ratios. The maximum luminance and current efficiency of the dual doping device has achieved 28180 cd/m2 and 4.7 cd/A, respectively. Meanwhile the values of the traditional LiF/Al cathode device are 12320 cd/m2 and 3.7 cd/A. Meanwhile, the maximum current efficiency of the dual LiF doping device decreases only by 25%. However, that of the traditional LiF/Al cathode device decreases by 46%. Such improved properties can be attributed to the enhanced carrier injection and transporting, and the balanced numbers of holes and electrons injected to the emitter layer due to the LiF dual doping effects.2. High work function, smooth morphology, transparent conducting oxide (TCO): manganese doped indium oxide (IMO) as anodes for OLEDs. IMO is one kind of multifunction TCOs, and has been applied in spintronics, gas sensor and humidity sensor. However, the reported IMO exhibited the high resistivity properties that hampered its applications in optoelectronics area. In this thesis, the IMO film was deposited on glass substrate by End-Hall ion-assisted (EHIAD) electron beam evaporation technique. Comparing with ITO, IMO anode has a higher work function (WF) of 5.35 eV (4.8 eV of ITO) and a superior surface morphology with an average roughness of 1.1 nm (2.4 nm of ITO). Furthermore, a high average optical transmittance of 87.2% in the visible region and a maximum optical transmittance of 92% at 460 nm could be achieved for the IMO film. The resistivity of IMO is only 7.08×10-4 ??cm, and the electron concentration and mobility are as high as 2.033×1020 cm-3 and 43.4 cm2/Vs, which is comparable to those of commercial ITO. The IMO anode OLEDs exhibits excellent hole injection ability and low operate voltage. The efficiency and luminance of OLEDs have been significant improved by using IMO anode instead of ITO anode.3. Organic solar cell with a novel ytterbium fluoride (YbF3) doped indium oxide (IYFO) anode. In this thesis, the IYFO film was deposited on glass substrate by electron beam evaporation associated with an EHIAD technology. The electrical and optical properties of IYFO are comparable to those of commercial ITO, and the stable high work function and smooth surface morphology could be achieved in IYFO films. Furthermore, a room temperature near-infrared photoluminescence (PL) with a peak at 1000 nm could be observed in IYFO. The high work function of IYFO anode gives a well energy alignment between anode and P3HT:PCBM active layer, which is helpful to hole collection, and increases the open voltage (Voc). The smooth surface of IYFO leads to a low defect density at the anode/organic interface, which decrease the recombination of hole and electron pairs and improved Fill Factor (FF). The high transmittance of IYFO is propitious to light absorption of OSC, which improves short current density (Jsc). Therefore, organic bulk heterojunction OSC based on P3HT:PCBM active layer and IYFO anode shows a efficiency of 2.3%, which increases 59% compared with those of traditional ITO anode OSC.4. Electroluminescence (EL) of C60 film with a current density- tunable- spectrum. Double hole and electron transporting layers OLED using C60 film as the light emitting layer has been fabricated in this thesis. In this device, 0.5 nm thick WO3 is used as the anode buffer layer to reduce the barrier height between ITO anode/organic interface. 20 nm thick TCTA and 30 nm thick CBP are used as the first and the second HTL, respectively. 35 nm thick TPBI and 60 nm thick C60 are used as the first and the second ETL, respectively. The double carrier transporting layer structure of this device effectively decreases the barrier height of interface and improves the carrier injection and transporting of OLED. The excellent carrier injection and transporting abilities of this device depresses the high symmetrical configuration of C60 molecule, and breaks the forbidden transitions from the lowest excited state to the ground state of C60 molecule. Broad electroluminescent spectra with three main peaks at 380 nm, 511nm, and 735 nm could be observed for the first time in C60 film. Furthermore, the emission color of the C60 OLED changes gradually from purple, blue to green, red and white color with the increase of current density. |
PDF Full Text Request