Colour Electronic Information Displays (EIDs) typically consist of pixels that are made up of red, green and blue (RGB) subpixels. A recent technology, Organic Light Emitting Diode (OLED), offers the potential to create a superior EID. OLED is already suitable for use in small displays and microdisplays for personal electronics products. OLED microdisplays, in particular, exhibit lower power consumption than equivalent direct-view panels thus enabling microdisplay-based personal display systems such as electronic viewfinders and video glasses to exhibit the longest possible battery life. In many EIDs, the light source is white and colour filters are used, at the expense of much absorbed light, to create the RGB light in the subpixels. Hence, the concept has recently emerged of adding a white (W) subpixel to form an RGBW pixel. The advantages can include lower power, higher luminance, and in the case of emissive displays, longer lifetime. One key to realizing the improved performance of RGBW EIDs is a suitable method of data conversion from standard RGB input signal formats to RGBW output signal formats. An OLED microdisplay built on Complementary Metal–Oxide–Semiconductor (CMOS) active matrix back-plane exhibits low power consumption. This device architecture also gives the OLED microdisplay the potential to realize the concept of low-power Display System on a Chip (DSoC). In realizing the performance potential of DSoC on an RGBW OLED microdisplay, there is a trade-off between system resources used to perform the data conversion and the image quality achieved. A compact and efficient method of RGB-to-RGBW data conversion is introduced to fit the requirement of “minimum system resources with indistinguishable visual side-effect” that is appropriate for an OLED microdisplay. In this context, the terms “Compact” and “Efficient” mean that the data conversion functionality (i) is capable of insertion into the signal path, (ii) is capable of integration on the OLED microdisplay back-plane, i.e., is small and (iii) consumes minimal power. The image quality produced by the algorithm is first simulated on a software platform, followed by an optical analysis of the output of the algorithm implemented on a real time hardware platform. The optical analysis shows good preservation of colour fidelity in the image on the microdisplay so that the proposed RGB-to-RGBW data conversion algorithm delivers sufficiently high image quality whilst remaining compact and efficient to meet the development requirements of the RGBW OLED microdisplay with DSoC approach.

In this work the electrochemical and spectroelectrochemical properties of a series of pi-conjugated organic polymers were studied. The polymers were deposited on platinum electrodes or ITO-coated glass substrates by potentiodynamic electro-polymerisation of the corresponding monomeric precursor molecules. The electro-chemical and photophysical properties of the triarylborane monomers were studied in detail in order to estimate possible influences on the behaviour of the corresponding polymer. The first part of this work aimed at the synthesis and investigation of conjugated donor–acceptor polymers which combine the prerequisites of an OLED within one material: the transport of positive and negative charges and the formation of emissive excited states. With the carbazole-substituted oxadiazoles 1–3 it was shown that on the one hand the carbazole functionality is suitable for enabling the electrochemical polymerisation of the monomers and on the other hand it facilitates reversible p-doping of the resultant polymers. Although n-doping of poly-1–poly-3 is possible due to the electron-deficient oxadiazole rings, it causes the continuous degradation of these electron-acceptor units. Interestingly, this process does not influence the capability of p-doping of the polymers. With respect to its electrochemical and spectroelectrochemical properties the behaviour of the borane polymer poly-4 is absolutely identical with that of the oxadiazole polymers. Moreover, the optical excitation of poly-4 in the solid state leads to the emission of blue-green light which suggests that this polymer might also possess electroluminescent properties. AFM-measurements of poly-4 films on ITO-coated glass substrates revealed, that the film thickness can be controlled to a certain extent by the number of polymerisation redox cycles. It was shown from the electrochemical and photophysical properties of the triarylboranes 4–6 that the pi–pi-interaction between boron and nitrogen atoms is comparably weak in these molecules. This leads to an unexpected ground-state polarisation with a partially positive boron atom and a partially negative nitrogen atom. Moreover, it was found that TAB 4 possesses a lower symmetry than D3 in solution and that excitation energy can be transferred amongst the three subchromophores of 4. By titration experiments it was also demonstrated that TAB 4 can reversibly bind fluoride ions and that the binding event significantly influences the optical absorption characteristics of the chromophore. It can be assumed, that the above mentioned properties, which have a profound influence on the photophysical behaviour of these triarylborane chromophores, also determine the behaviour of the corresponding polymer in a solid state environment. The aim of the second part of this work was the investigation of purely n-conducting materials based on electron-deficient borane and viologen polymers. The corresponding precursor molecules should be polymerised on platinum electrodes by reductive electropolymerisation. However, a reductive polymerisation was not possible for the borane monomer 19 which is thought to be due to a strong localisation of the unpaired electron on the central boron atom of the radical anion. An electropolymerisation of the cyano-substituted bispyridinio-compound 17 failed because of the poor quality of CN– as a leaving group. Thus, a synthesis of the analogous isomer 18 was developed, in which the cyano-substituents were exchanged by the better leaving group Cl–. The viologen polymer poly-18, which can be regarded as an electron-deficient iso-electronic analogue of poly(para-phenylene), was successfully deposited on a platinum electrode by reductive electropolymerisation of 18. Poly-18 can be reversibly n-doped at comparably low potentials; however, at higher potentials the polymer is overcharged and destroyed irreversibly. As the synthetic strategy for 18 allows the variation of both spacer unit and leaving group in the last two steps of the reaction sequence, a series of analogous compounds can be easily synthesised using this route. / Im Rahmen der vorliegenden Arbeit wurden die elektrochemischen und spektroelektrochemischen Eigenschaften einer Reihe von pi-konjugierten organischen Polymeren untersucht. Die Polymere wurden durch potentiodynamische Elektropolymerisation der entsprechenden monomeren Vorläufermoleküle auf Platinelektroden bzw. ITO-beschichteten Glassubstraten abgeschieden. Im Falle der Triarylborane wurden die elektrochemischen und photophysikalischen Eigenschaften der Monomere genauer untersucht, um mögliche Einflüsse auf das entsprechende Polymer abschätzen zu können. Der erste Teil dieser Arbeit zielte auf die Synthese und Untersuchung von konjugierten Donor-Akzeptor-Polymeren ab, die die Grundvoraussetzungen für OLEDs in einem Material vereinen: den Transport von positiven und negativen Ladungen sowie die Bildung von emittierenden angeregten Zuständen. Anhand der Carbazol-substituierten Oxadiazole 1–3 konnte gezeigt werden, dass die Carbazol-Funktionalität einerseits geeignet ist eine elektrochemische Polymerisierbarkeit der Monomere zu gewährleisten und andererseits eine reversible p-Dotierung der resultierenden Polymere möglich macht. Eine n-Dotierung der Polymere poly-1–poly-3 ist aufgrund der elektronenarmen Oxadiazol-Ringe zwar möglich, führt aber zum schrittweisen Abbau dieser Akzeptor-Eiheiten. Interessanter-weise lassen sich die Polymere aber weiterhin p-dotieren. Hinsichtlich seiner elektrochemischen und spektroelektrochemischen Eigen-schaften weißt das Boran-Polymer poly-4 ein zu den Oxadiazol-Polymeren absolut identisches Verhalten auf. Darüber hinaus konnte gezeigt werden, dass die optische Anregung von poly-4 im Festkörper zur Emission von blau-grünem Licht führt, was die Vermutung nahe legt, dass dieses Polymer auch elektrolumineszierende Eigenschaften besitzen könnte. AFM-Messungen an Filmen von poly-4 auf ITO-beschichteten Glassubstraten ergaben weiterhin, dass sich die Schichtdicke des Polymers durch die Anzahl der Polymerisationszyklen in einem gewissen Bereich einstellen lässt. Anhand der elektrochemischen und photophysikalischen Eigenschaften der Triarylborane 4–6 konnte gezeigt werden, dass die pi-Konjugation zwischen den Bor- und Stickstoff-Atomen in diesen Molekülen sehr gering ist. Dies führt zu einer ungewöhnlichen Grundzustandspolarisation mit partiell positivem Bor und partiell negativem Stickstoff. Darüber hinaus wurde festgestellt, dass das Triarylboran 4 in Lösung eine geringere Symmetrie als D3 aufweißt und dass die durch eine optische Anregung aufgenommene Energie entlang der identischen Subchromophore von 4 übertragen werden kann. Durch Titrationsexperimente konnte außerdem gezeigt werden, dass 4 Fluoridionen reversibel binden kann, wobei sich das optische Absoptionsverhalten des Chromophors deutlich ändert. Es kann angenommen werden, dass die genannten Eigenschaften, die sich entscheidend auf das photophysikalische Verhalten dieser Triarylboran-Chromophore auswirken, auch die Eigenschaften des entsprechenden Polymers im Festkörper beeinflussen. Im zweiten Teil dieser Arbeit sollten reine n-Leiter Materialien auf der Basis von elektronenarmen Boran- bzw. Viologen-Polymeren untersucht werden. Die entsprechenden Vorläufermoleküle sollten dabei durch reduktive Elektro-polymerisation auf Platinelektroden polymerisiert werden. Im Falle des Boran-Monomers 19 war eine reduktive Polymerisation nicht möglich, was vermutlich auf eine starke Lokalisierung des ungepaarten Elektrons auf dem zentralen Boratom des Radikalanions zurückzuführen ist. Bei der Cyano-substituierten Bispyridinio-Verbindung 17 scheiterte eine reduktive Elektro-polymerisation an der schlechten Qualität von CN– als Abgangsgruppe. Daher wurde eine Synthese für das analoge Isomer 18 entwickelt, bei dem die Cyano-Substituenten gegen die bessere Abgangsgruppe Cl– ausgetauscht wurden. Durch reduktive Elektropolymerisation von 18 konnte das entsprechende Viologen-Polymer, welches als elektronenarmes isoelektronisches Analogon zu Poly(para-phenylen) angesehen werden kann, auf einer Platinelektrode abgeschieden werden. Das Viologen-Polymer poly-18 kann bereits bei relativ niedrigen Potentialen reversibel n-dotiert werden, bei zu hohen Potentialen wird das Polymer jedoch überladen und irreversible zerstört. Da es die für 18 verwendete Synthesestrategie erlaubt, sowohl die Spacereinheit als auch die Abgangsgruppe in den letzten zwei Reaktionsschritten zu variieren, sind auf diesem Weg weitere analoge Verbindungen leicht zugänglich.

abstract: Organic electronics have remained a research topic of great interest over the past few decades, with organic light emitting diodes (OLEDs) emerging as a disruptive technology for lighting and display applications. While OLED performance has improved significantly over the past decade, key issues remain unsolved such as the development of stable and efficient blue devices. In order to further the development of OLEDs and increase their commercial potential, innovative device architectures, novel emissive materials and high-energy hosts are designed and reported. OLEDs employing step-wide graded-doped emissive layers were designed to improve charge balance and center the exciton formation zone leading to improved device performance. A red OLED with a peak efficiency of 16.9% and an estimated LT97 over 2,000 hours at 1,000 cd/m2 was achieved. Employing a similar structure, a sky-blue OLED was demonstrated with a peak efficiency of 17.4% and estimated LT70 over 1,300 hours at 1,000 cd/m2. Furthermore, the sky-blue OLEDs color was improved to CIE coordinates of (0.15, 0.25) while maintaining an efficiency of 16.9% and estimated LT70 over 600 hours by incorporating a fluorescent sensitizer. These devices represent literature records at the time of publication for efficient and stable platinum phosphorescent OLEDs. A newly developed class of emitters, metal-assisted delayed-fluorescence (MADF), are demonstrated to achieve higher-energy emission from a relatively low triplet energy. A green MADF device reaches a peak efficiency of 22% with an estimated LT95 over 350 hours at 1,000 cd/m2. Additionally, a blue charge confined OLED of PtON1a-tBu demonstrated a peak efficiency above 20%, CIE coordinated of (0.16, 0.27), and emission onset at 425 nm. High triplet energy hosts are required for the realization of stable and efficient deep blue emission. A rigid “M”-type carbazole/fluorene hybrid called mDCzPF and a carbazole/9-silafluorene hybrid called mDCzPSiF are demonstrated to have high triplet energies ET=2.88 eV and 3.03 eV respectively. Both hosts are demonstrated to have reasonable stability and can serve as a template for future material design. The techniques presented here demonstrate alternative approaches for improving the performance of OLED devices and help to bring this technology closer to widespread commercialization. / Dissertation/Thesis / Doctoral Dissertation Materials Science and Engineering 2019

Bis(2-methyl-8-quinolinolato)-(2,6-dimethylphenolate)aluminum is a newly synthesized material suitable for manufacturing organic light-emitting devices (OLED). NMR parameters such as chemical shift, dipolar and quadrupolar tensors are intimately related to the electronic and geometric structures which are important for understanding its physical and chemical properties. In this work, we report the solid state NMR studies of this material. By using two-field (corresponding to proton resonance frequencies of 200 MHz, 500 MHz , respectively) 1D 1H MAS, 27Al MAS, 1H/13C CP/MAS and 2D 13C nutation MAS techniques, the chemical shift tensors of 13C and quadrupolar coupling constant of 27Al have been obtained. The relationship between these values and the light-emitting properties of this material is discussed.

In this present paper, the electrical characteristics of the interface between the cathode and organic layer in OLEDs are discussed. The dipole formed between the cathode and organic layer are the dominant factor resulting in the electrical characteristics of OLEDs. However, based on the Al/LiF/Alq3 architecture published by the Kodak company, it is mainly because that by inserting a LiF layer lead to change the interface characteristic of Al/Alq3 as to changed the chemical reaction occurred at the interface of Al/Alq3. The LiF interlayer could enable the contact interface being depolarized and the work function being close to the vacuum level, therefore, it will reduce the electron injection barrier to improve the OLED performance. In addition, the increase luminous efficiency was due to that without generating any gap state and interdiffusion occur at the interface of Al/LiF/Alq3. For the carrier injection model reported by several authors, the carrier injection process is summarized by two steps as follow: first, the inject carriers translate from metal Fermi level to the energy distribution of interface. Second, inject carriers translate from the energy distribution of interface to the energy distribution of organic layer, afterward, the inject carriers migrate with hopping conduction in the organic level. Hence, it will regards to the dependence of the variety of LiF thickness on the influence of the injection model, and assume that as LiF thickness is 0.5 nm the device could be able to have the best performance, and also assume that LiF was able to decompose equal number of Alq3- and the Li+ ions at the interface of Al/LiF/Alq3 contact, and that led to form a voltage in the LiF layer. Finally, we found that the simulation approaches were consistent with the experimental results very well.

The top emission organic light-emitting diodes (TEOLEDs) with multilayer electrodes were studied. Firstly a high reflectivity metal, Al, followed by a high work function metal, such as Pt, Ni or Au, was used as bilyaer anode. It was found that the Al/Au bilayer anode can give rise to a very good luminescent performance if the Al thickness in the bilayer was adjusted to 70 nm. The Al/Au bilayer anode has high reflectivity and good adhesive contact with the hole injection layer. Next the cathode in TEOLEDs composed of multiple layers, LiF/Al/Ag, were studied. The optimum thicknesses in each layer as 0.4/4/15 nm were used to achieve high transparency and good conductivity. The effects of thicknesses of each organic layer were also studied. When the optimum thicknesses of m-MTDATA/NPB/Alq3 were adjusted to 20/40/60 nm, the highest brightness and best luminance efficiency of 8041 cd/m2 and 3 cd/A, respectively, were obtained. The white TEOLED was also studied in this thesis. The ADS082BE was blue host-emitting material and DCJT was orange guest-emitting material. The doped concentration and location were adjusted to control the blue to orange luminance intensity ratio. A white emission with CIE coordinate (0.30, 0.34) was obtained. The highest luminance of 3739 cd/m2 @13.5 Vand best luminance efficiency of 3 cd/A@10V were obtained in the white TEOLED which used multilayer anode and cathode structures. Finally TEOLEDs were also fabricated on the Si wafer and flexible substrate. The brightness and luminance efficiency were (3894 cd/m2;3.8 cd/A on Si wafer),(575 cd/m2, 1.46 cd/A on PES substrate).

New generation of Flat Panel Displays, Organic Light Emitting Diode (OLED) with fast response, high brightness, high contrast plays an important role gradually in the further market of flat penal display (FPD). The characteristics of OLED like as bright light¡Bthin¡Bshort¡Bsmall subverts the concept of LCD displays. But the life time of organic materials become the obstruction on the further development of OLED-FPD. In addition, the non-uniformity of OLED Panel could cause the quality of frames worse. Hence, for solve the problem, A more powerful Pixel driving circuit will be designed for achieving the high performance of OLED based FPD. Recently, many researches were related to the compensating pixel driving circuits have reported. The catalogs of pixel driving circuits were divided into two types as voltage-driving circuit and current-driving circuit, which were used to solve the problems like the variation of the threshold voltage, the electronic mobility and the long time with storing capacitors charge and discharge. In this study, a novel pixel driving circuit with new discharged paths was design in order to solve the long time of charge and discharge. Theoretical and circuit simulation show this design can enhance the frame rates effectively. At the same time, it also achieves better performance such as higher resolution and quality of frame rate for the large size OLED panels.

Three subjects on the organic light-emitting diodes (OLEDs) have been studied. First, We inserted a NPB¡GAlq3 mixed layer between these two NPB and Alq3 layers to decrease the holes mobility and improve the combined efficiency between the holes and electrons. After inserting the NPB¡GAlq3 layer, the current density of the device( ITO/ MTDATA¡]5 nm¡^/ NPB¡]60-Y¡^nm¡^/NPB¡GAlq3 (Z wt%)(Y nm) / Alq3¡]60 nm¡^/ LiF(0.7 nm)/ Al(180 nm)) is decreased obviously. This result suggests that NPB¡GAlq3 layer could delay the holes mobility. The optimum concentration in our device is 30 wt% while the total thickness is 30nm. Then we combined NPB and Rubrene to obtaine white emission and fabricate a white organic light emitting diode (WOLED). The structure of WOLEDs is ITO/ MTDATA/ NPB/ NPB:Rubrene/ TPBI/ LiF/ Al. By change the concentration of NPB:Rubrene layer, the WOLED can emit white light. We can get the maximum luminance efficiency of 9.0 cd/A at 20.8mA/cm2 with 1 wt%. And the device emit greenish-white. In order to get higher efficiency and pure light WOLED, we use the grading structure to prepare OLED. The structures are device A: ITO/ MTDATA(5nm)/ NPB(10nm)/ NPB:Rubrene1%(25nm)/ NPB:Rubrene 0.5%(25nm)/ TPBI(60nm)/ LiF(0.7nm)/Al (180nm); device B: ITO/ MTDATA(5nm)/NPB(10nm)/NPB:Rubrene2%(17nm)/ NPB:Rubrene1% (17nm)/NPB:Rubrene0.5%(17nm)/TPBI(60nm)/ LiF(0.7nm)/ Al (180nm) We get the maximum luminance of 17270 cd/m2 and 24280 cd/m2 , respectively and the optimum efficiency of 16.1 cd/A and 18.5 cd/A, respectively. The CIE coordinate of the device is x=0.35, y=0.36, which is identical to white light.

In this research, we used the novel material 9-cyano-10-(2-benzothiazoly1)-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro- 1H,5H,11H- benzo[l]pyrano[6,7,8-ij]quinolizin-11-one(RC545T) as a red dopant, which was synthesized from the green dopant material 10-(2-benzothiazoly1)-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro- 1H,5H,11H- benzo[l] pyrano[6,7,8-ij]quinolizin-11-one(C545T). First, we used aluminum tris(8-hydroxyquinoline)(Alq3) as a hostmaterial and doped with different concentration of RC545T, with the configuration of ITO(1300Å)/NPB(650Å)/Alq3:x%RC545T(300Å)/Alq3(300Å)/LiF(8Å)/Al(2500Å). We obtained the maximum efficiency at 2% of RC545T. Second, 5,6,11,12-Tetraphenylnaphthacene (rubrene) and RC545T as a co-dopant material were doped into the Alq3 layer. The energy transfer from Alq3 to RC545T was mainly assisted by Rubrene. Therefore, we obtained the luminance yield of 0.54 cd/A under the current density of 20mA/cm2, and the peak emission wavelength at 632nm with a CIExy color coordinate of (0.642,0.347).The improved color purity render RC545T a good red-emitting dopant in OLED application.

In this thesis we proposed two new pixel circuits for organic light emission display. The first one is 5T1C circuit with two control signals. It can compensate threshold voltage variation and the drop of the power supply voltage that result in OLED current non-uniformity. We have demonstrates that the pixel circuit has high immunity to the threshold voltage variation. In addition, the circuit uses low supply voltage compared with the conventional 5T1C pixel circuit, so it is a low power driver circuit. The second one employs the voltage feedback method and uses the gain value of design circuit for compensating the threshold voltage shift of the driving TFT.To the aim is to reach that to the flow through current of the driving TFT have no relationship with the threshold voltage of TFT. Thus, the OLED can emission light with retaining uniformity light in each time. Because the proposed circuit configuration has low supply voltage and low select pulse voltage, the spike wave phenomenon can be improved and eliminated while the circuit switchs on and off. Due to the circuit supply voltage is decreased, it power consumption reduce significantly and the capacitor charging time is less than 70 £gs. Thus, in this thesis, the two proposed pixel circuits are both of low voltage and low power. The two pixel circuits designed have been fabricated by TSMC 0.35£gm 2P4M CMOS technology with 3.3v power supply. The 5TIC chip area is 1031.8 ¡Ñ 1083.7£gm2 and the measured result shows that when the select pulse is 0~10V, the input voltage is 10V, the select pulse2 is 0~8V and the Vdata¡@voltage range is 0~5V, the OLED current is correspond to 0~20.6£gA and the maximum power consumption is 17£gw. The chip area of the voltage feedback circuit is 1083.38 ¡Ñ 1149.8£gm2 and the measured result shows that when the select pulse is 0~10V, the input voltage is 10V and the feedback resistor is 50£[, the power consumption is 72£gw and the charging time is 51.7£gs.