Shou-Cheng Dong

Blue organic light‐emitting diodes (OLEDs) continue to face significant challenges due to the scarcity of stable and efficient blue‐emitting materials. This study presents four fluorescent blue emitters based on a pyrene core with high photoluminescence quantum yield (PLQY) and longevity. By incorporating these emitters as dopants in anthracene‐based hosts with highly efficient triplet–triplet annihilation, we achieved blue OLEDs with a maximum external quantum efficiency (EQE) of 8.9% and a champion LT ₇₀ lifetime (decay to 70% of an initial luminance at 1000 cd/m ² ) of 111.6 h. Furthermore, we combined the blue emitters with yellow, green, and red phosphorescent emitters to obtain white OLEDs with a maximum EQE of 17.2% and a color rendering index of 88. Our results highlight the potential of these blue emitters in boosting the performance of both blue and white OLEDs.

Usually, the resolution loss is severe in light‐field display due to the spatial multiplexing of several neighboring pixels to display images from different directions. However, limited by the resolution of the flat panel display, the light‐field 3D display shows insufficient display size, 3D image depth, or resolution. This article uses optimized ferroelectric liquid crystal (FLC) shutters with high contrast (~1000:1), ultra‐fast response (<20 μs), and polarity‐related binary switching at low operating voltage (5 V). This article utilized 32 time‐sequentially opened FLC light valve arrays refreshed at 2 kHz to display images from different directions. Because of the polarity‐sensitive switching nature of FLC, the reverse phase induces serious crosstalk between different images. This work uses the timing synchronization method of dual‐FLC liquid crystal cells to achieve independent control of 32 light valves without reverse phase, reducing the crosstalk and increasing the equivalent 3D resolution by multiplexing the flat panel display 32 times within 60 Hz.

Introducing molecular chirality into perovskite crystal structures has enabled the control of carrier spin states, giving rise to circularly polarized luminescence (CPL) in thin films and circularly polarized electroluminescence (CPEL) in LEDs. Spin-LEDs can be fabricated either through a spin-filtering layer enabled by chiral-induced spin selectivity or a chiral emissive layer. The former requires a high degree of spin polarization and a compatible spinterface for efficient spin injection, which might not be easily integrated into LEDs. Alternatively, a chiral emissive layer can also generate circularly polarized electroluminescence, but the efficiency remains low and the fundamental mechanism is elusive. In this work, we report an efficient green LED based on quasi-two-dimensional (quasi-2D) chiral perovskites as the emitting layer (EML), where CPEL is directly produced without separate carrier spin injection. The optimized chiral perovskite thin films exhibited strong CPL at 535 nm with a photoluminescence quantum yield (PLQY) of 91% and a photoluminescence dissymmetry factor (g_lum) of 8.6 × 10^-2. Efficient green spin-LEDs were successfully demonstrated, with a large EL dissymmetry factor (g_EL) of 7.8 × 10^-2 and a maximum external quantum efficiency (EQE) of 13.5% at room temperature. Ultrafast transient absorption (TA) spectroscopic study shows that the CPEL is generated from a rapid energy transfer accompanied by spin transfer from 2D to 3D perovskites. Our study not only demonstrates a reliable approach to achieve high performance spin-LEDs but also reveals the fundamental mechanism of CPEL with an emissive layer of chiral perovskites.

This research investigates the impact of deuteration on the operational lifetime of blue organic light‐emitting diodes (OLEDs). Our study focuses on the kinetic isotope effect (KIE) and how it enhances device lifetime. Specifically, we examine the effects of deuteration on OLEDs with emitters based on common polycyclic aromatic hydrocarbons by deuterating anthracene‐based host materials. Our findings show that the deuterated analogues with incremental deuterium substitutions exhibit similar electroluminescence (EL) performances but progressively prolonged device lifetimes as a function of deuteration, indicating a cumulative enhancement effect. We observed a twofold increase in device lifetime with partial deuterium substitutions, while highly deuterated hosts realized up to a fourfold improvement. Furthermore, we found that device degradation is initiated from the interface of the hole transport layer (HTL) and emitting layer (ETL), and deuteration can mitigate the degraded reactions in the devices, thereby improving operational stability. These results provide insight into how deuteration can increase the operational lifetime of OLEDs, which has important implications for developing more efficient and durable OLED materials.

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Significant lifetime enhancement, up to an eight-fold increase in T₉₀, has been demonstrated in blue organic light-emitting diode (OLED) devices through the deuteration of host and hole transport materials. We observed a progressive increase in T₉₀ using a series of anthracene-based hydrocarbon hosts with incremental deuteration in the emitting layer. In addition, we realized further lifetime improvement using a deuterated hole-transport layer along with the deuterated emitting layer. To elucidate the deuteration effects, we utilized laser desorption/ionization-time-of-flight (LDI-TOF) mass spectrometry for in situ UV irradiation to induce photodegradation and immediate chemical analysis of the resultant photodegradation species. Adducts between the host and moieties from transport materials were identified in UV-degraded films comprising a mixture of host and transport materials, indicating that similar species could be produced in OLED devices using these materials. Deuteration, in effect, mediated the formation of these adduct species, presumably electroluminescence quenchers, and thus improved the device lifetime. An approximate agreement was obtained between the kinetic isotope effect of the photodegradation reactions and the enhancement in device lifetime with deuteration.

The successful implementation of perovskite light-emitting diodes (PeLEDs) in advanced displays and lighting has proven to be challenging because of the inferior performance of blue devices. Here, we point out that a strained system would lead to the quasi-degenerate energy state to enhance the excited-state transition due to the formation of double-polarized transition channel. The tensile strained structure also brings about a synergetic control of the carrier dynamics in virtue of lattice structure deformation and reduced dimensional phase regulation to promote carrier population in large bandgap domains and to realize near-unit energy transfer from the large bandgap phases to the emitter phases. Accordingly, high external quantum efficiencies of 14.71 and 10.11% are achieved for the 488- and 483-nanometer PeLEDs. This work represents a versatile strategy using a strained system to achieve enhanced radiative emission for the development of efficient PeLEDs.