Photoluminescence from Two-Phase Nanocomposites Embedded in Polymers

A set of polymer-embedded, two-colored nanocomposites were prepared where the co-existing emission peaks (~578 nm and ~650 nm) had different ratios at their emission thresholds. The nanocomposite samples were simultaneously excited by a 405 nm laser, and the growth of photoluminescence intensities was studied as a function of excitation intensity. The two peaks showed different growth evolution mechanisms. The factors impacting this difference could be (1) energy transfer between the two sized nanoparticles; (2) relaxation mechanism of smaller nanoparticles; and (3) material properties of the polymer.

Advances in Solution-Processed OLEDs and their Prospects for Use in Displays

This review outlines problems and progress in development of solution-processed organic light-emitting diodes (SOLEDs) in industry and academia. Solution processing has several advantages such as low consumption of materials, low-cost processing, and large-area manufacturing. However, use of a solution process entails complications, such as the need for solvent resistivity and solution-processable materials, and yields SOLEDs that have limited luminous efficiency, severe roll-off characteristics, and short lifetime compared to OLEDs fabricated using thermal evaporation. These demerits impede production of practical SOLED displays. This review outlines the industrial demands for commercial SOLEDs and the current status of SOLED development in industries and academia, and presents research guidelines for the development of SOLEDs that have high efficiency, long lifetime, and good processability to achieve commercialization.

Improved Fluorescence and Gain Characteristics of Er-Doped Optical Fiber with PbS Nanomaterials Co-Doping

Er-doped optical fiber (EDF) with ultra-broad gain bandwidth is urgently needed given the rapid advancement of optical communication. However, the weak crystal field of the host silica glass severely restricts the bandwidth of traditional EDF at 1.5 μm. In this study, we theoretically explored the introduction of PbS nanomaterials in the silica network assisted with the non-bridging oxygen. This can significantly increase the crystal field strength of Er³⁺ ions in the local structure, leading to their energy level splitting and expanding the fluorescence bandwidth. Additionally, the PbS/Er co-doped optical fiber (PEDF) with improved fluorescence and gain characteristics was fabricated using modified chemical vapor deposition combined with the atomic layer deposition technique. The presence of PbS nanomaterials in the fiber core region, which had an average size of 4 nm, causes the ⁴I_13/2 energy level of Er³⁺ ions to divide, increasing the fluorescence bandwidth from 32 to 39 nm. Notably, the gain bandwidth of PEDF greater than 20 dB increased by approximately 12 nm compared to that of EDF. The obtained PEDF would play an important role in the optical fiber amplifier and laser applications.

High-performance inverted organic light-emitting diodes with extremely low efficiency roll-off using solution-processed ZnS quantum dots as the electron injection layer

The electron-injecting layer (EIL) is one of the key factors in inverted organic light-emitting diodes (OLEDs) to realize high electroluminescence efficiency. Here, we proposed a novel cathode-modified EIL based on ZnS quantum dots (QDs) in inverted OLEDs, and demonstrated that the device performance was dramatically improved compared to traditional ZnO EIL. The EIL of ZnS QDs may greatly promote the electron injection ability and consequently increase the charge carrier recombination efficiency for the device. We also investigated the effects of different pH values (ZnS-A, pH = 10; ZnS-B, pH = 12) on the properties of ZnS QDs. The best inverted phosphorescent OLED device employing mCP:Ir(ppy)₃ as the emission layer showed a low turn-on voltage of 2.9 V and maximum current efficiency of 61.5 cd A⁻¹. Also, the ZnS-A based device exhibits very-low efficiency roll-off of 0.9% and 4.3% at 1000 cd m⁻² and 5000 cd m⁻², respectively. Our results indicate that use of ZnS QDs is a promising strategy to increase the performance in inverted OLEDs.

The electron-injecting layer (EIL) is one of the key factors in inverted organic light-emitting diodes (OLEDs) to realize high electroluminescence efficiency.