This PDF file contains the front matter associated with SPIE Proceedings Volume 12208, including the Title Page, Copyright information, Table of Contents and Conference Committee list.

The efficiency performance of OLED devices has several key ingredients. And host material determines only the charge balance factor among them. While dopant material determines all the remaining dominants. So dopant material is very difficult to develop because there are many dominant factors to be tweaked or tinkered to maximize the device performance. To solve this problem, we have focused on building quantitative prediction models for each of the dominant factors. I will just present four quantitative prediction models we use to design the molecular structure in Samsung OLED displays.

Organic light-emitting diodes (OLEDs) are a promising light-emitting technology useful for various display applications^1,2. Despite great progress in this field^3-12, there is an ongoing challenge to realize high performance blue OLEDs with efficiency, good color purity, and device lifetime. Here, we report pure-blue (CIEx,y color coordinates of [0.13, 0.16]) OLEDs with high-efficiency (external quantum efficiency of 32 % at 1000 cd m^–2 ), narrow-emission (full width half maximum of 19 nm), and good stability (LT95 of 18 hours at an initial luminance of 1000 cd m–2 ). The design is based on a two-unit stacked tandem hyperfluorescence (HF)-OLED with an improved singlet-excited energy transfer process from a sky-blue TADF assistant dopant (AD) (HDT-1) to a pure-blue terminal emitter (TE) (v-DABNA). Furthermore, the effect of dopant concentration of terminal emitter on the device performance of hyperfluorescence OLEDs is studied. Device shows a better color purity when dopant concentration is increased. On the other hand, new hyperfluorescence OLEDs have been fabricated, in which device stability has been extended with a new molecular design of TE.

Perovskites is a very promising material that is being extensively studied at the bulk and nanosize scales because it has outstanding optical properties, including high quantum efficiency and narrow emission spectra. To realize a full-color display in the research field of perovskites or perovskite-structured quantum dots (PeQDs), the development of white-light-emitting devices that operate by emitting light of three primary colors (red, green, and blue) has emerged as an active research topic. In this presentation, we report for the first time three-color white-light emission with high brightness from white-emitting PeQD organic light-emitting diodes (WPeQD-OLEDs) fabricated using a PeQD material and organic emitters. The electroluminescence (EL) spectra of the WPeQD-OLEDs showed EL maximum peaks at 460, 527, and 640 nm; the CIE color coordinates of the emitted light were (0.33, 0.40). The EL results confirmed that the maximum luminance was 49,000 cd m−2 and the maximum luminance efficiency and power efficiency were 4.48 cd A−1 and 2.16 lm W−1 . Also, we achieved a new hybrid pink device of perovskite red QD (PRQD) and organic blue emitter (OBE) which have different emission mechanisms in bilayered LED devices. It has pink emission, CIE coordinate of (0.331, 0.204) which cannot be provided by a single emitter.

Micro-LED is emerging as a potential candidate for high-end display products with attractive properties like High contrast ratio, high resolution, small pixel size, longer life, wide colour gamut, the low power consumption etc. Two dominating methods for Micro-LED fabrication are mass transfer and colour conversion. Colour conversion can be achieved by colour converting materials such as quantum dots (QDs) or light-emitting polymers. More efficiency and light intensity can be achieved using this colour conversion technique as compared to the mass transfer technique. The colour conversion technique works with a GaN-based blue colour chip and we don’t require the other two-colour diode chips which will ultimately save time and production cost by avoiding mass transfer for the fabrication of Micro-LED. In this experiment, we evaluated organic dye for red (DCJTB) and green (C545T) emitters in a water-resistant, strong binder like PVB as a host material under different solvents resulting in rare-earth element-free fluorescent films. These polymers generally contain polyols that have long chains of carbon and can be extended into the solvent easily and they act as an anchoring group. PVB being water repellent helps in moulding the film with higher efficiency (~ 90%) and enhanced stability under normal and humid conditions, resolving the issue of device degradation in the presence of water content in the case of OLED. The synthesis process is very simple, cost-effective, and non-toxic.

Efficiency limiting factors of quantum dots light-emitting diodes (QLEDs) are studied by a machine learning approach using features taken from published data. Prototypical structure of Cd-based QLEDs is transparent conductive oxide (TCO)/hole transport layer (HTL)/quantum dots (QDs)/electron transport layer (ETL)/Al, fabricated by printing processes. The most important factor is the hole injection barrier from HTL to QD layer (about 1 eV in CdSe QLEDs). A mechanism of the hole injection in such QLEDs is discussed using device simulation, and the experimental results that support the mechanism are shown. In addition, other efficiency limiting factors - the electron mobility of HTL and carrier balance in QD layer - are experimentally shown.

Polyethylenimine (PEI) is sometimes used as a passivation layer at the interface between ZnO electron transport layer and quantum-dots emission layer in quantum-dots light emitting devices (QDLEDs). We recently find that blending ZnO with PEI (ZnO:PEI) is advantageous over using it in a separate layer in terms of device stability. In this work, a comparative study between the ZnO:PEI with a neat ZnO ETL is conducted. The ZnO:PEI ETL results in improvement in both EQE and lifetime of QDLEDs compared to the ZnO ETL. By replacing the ZnO ETL with the ZnO:PEI ETL, delayed EL measurements reveal changes in charge distribution across the QDLED. Applying a reverse bias pulse shows that the reversible delayed EL components in the QDLED with the ZnO:PEI ETL stemmed from the electrons placed in a hole transport layer (HTL). The electrons in the HTL induce an annihilation of accumulated holes at the QD EML/HTL that can be a cause of device degradation. The result provides a new insight into the importance of managing charge distribution across the QDLED via ZnO ETL modification for realizing highly stable QDLEDs.

Metal-dielectric photonic crystals (MDPCs) represent a class of photonic structures which offer unique types of control over the propagation of light. Recent work has demonstrated the ability to form MDPCs using stacked microcavity OLEDs, which enable the generation of complex electroluminescence profiles consisting of multiple emission peaks. Here, we analyze the photonic band formation of idealized MDPCs. We systematically examine the impact of materials parameters on the density of states of the photonic bands and transmission losses through the crystal. We demonstrate the formation and collapse of a Peierls band-gap and the breakdown of the unit cell approach.

Stimulated emission is observed from OLEDS at current densities as low as 20 uA/cm2, where a high Q cavity is formed between the Ag cathode and the exit surface of the substrate. Inversion is dependent on Boltzmann population of vibrational levels serving as the ground state and this results in spectral dynamics on the time scale of thermalization of the device.

Preferential alignment of molecular permanent dipole moments, known as spontaneous orientation polarization (SOP), is present in many materials employed in the active layers of organic light-emitting devices (OLEDs). This phenomenon leads to the formation of bound polarization charge, which is compensated by polaron accumulation at voltages below turn-on. While most prior work has focused on polarization in the device electron transport layer (ETL), here we examine the impact of emissive layer SOP by systematically probing polaron accumulation and exciton-polaron quenching in phosphorescent OLEDs. To gain a deeper understanding of polaron accumulation, device capacitance is systematically probed as a function of voltage across samples with polar and nonpolar emissive layers. We find that capacitance measurements can be used to track not only the number of accumulated charges, but also its location within the device active layers. This study provides an analysis framework that allows further insights on the charge accumulation process in OLEDs, thus improving our understanding of SOP in OLEDs

Using the density functional theory, a first-principle approach, the structural, electronic, and optical properties of the double perovskites A2BX6 (A= Cs; B=Sn; X=Cl, Br, and I) were calculated. Calculated parameters lattice constants and band gaps agree with experimental and theoretical observations. The band gap of the A2BX6 compounds is within the optimal range for single-junction photovoltaic applications. The ideal band gap, high dielectric constants, and optimum light absorption of these perovskites make them suitable for high performance single and multi-junction perovskite solar cells