Yibo Chen

A bright and moisture-resistant red-emitting Lu3Al5O12:Mn4+,Mg2+ garnet phosphor for high-quality phosphor-converted white LEDs

The rational and delicate synthesis of Mn4+ activated red-emitting oxide phosphors with high photoluminescence quantum yield (PLQY) and photo-stability for developing high-quality w-LEDs still remains a great challenge. Herein, we demonstrate a simultaneous ion co-substitution design strategy to synthesize a red-emitting Lu3Al5O12:Mn4+,Mg2+ garnet phosphor delicately with the assistance of MgF2. The Mn4+ activated garnet phosphor exhibits superior moisture resistance properties and high PLQY (ca. 72.41%), which emits a bright and narrow-band red light peaking at ∼670 nm due to the 2E–4A2 spin-forbidden transition of Mn4+ upon UV excitation. Remarkably, MgF2 as a charge compensator & flux can not only accelerate the solid state reaction, but also greatly improve the emission intensity. Furthermore, by employing the as-prepared Lu3Al5O12:Mn4+,Mg2+ as a red component, we fabricate a warm w-LED with a high color rendering index (Ra = 81.4) and low color temperature (CCT = 4766 K) based on a UV chip and commercial blue and yellow phosphors.

VUV/Vis Photoluminescence, Site Occupancy, and Thermal‐Resistance Properties of K4SrSi3O9:Ce3+

A series of Ce3+ -activated K4 SrSi3 O9 materials emitting bright blue light under near-UV excitation was obtained by a facile solid-state reaction. The luminescence of Ce3+ -doped K4 SrSi3 O9 shows excellent thermal stability in a large temperature range. The detailed temperature/concentration-dependent luminescent properties of Ce3+ confirm that there are two different Ce3+ sites in K4 SrSi3 O9 :Ce3+ , and energy transfer from the high-energy Ce(1)3+ sites to the low-energy Ce(2)3+ sites was demonstrated to occur by electric dipole-dipole interaction. The maximum photoluminescence quantum yield of Ce3+ -doped K4 SrSi3 O9 can reach 56 %, and a UV-excited white LED device with low correlated color temperature (CCT=4617 K) and high color-rendering index (Ra =80) was fabricated with K4 SrSi3 O9 :Ce3+ .

Hybrid Organic-inorganic Lead Bromide Perovskite Supercrystals Self-Assembled with L-cysteine and Their Highly Luminescent Properties

The introduction of functional ligands that are beneficial for the assembly of perovskite nanocrystals (PNCs), has opened up new avenues for the fabrication of highly efficient optoelectronic and photovoltaic devices. In this work, self-assembled organic–inorganic hybrid lead bromide perovskite cubic supercrystals have been synthesized via a wet chemistry approach using trifunctional L-cysteine as capping ligands. These supercrystals were enhanced 6.9 times compared to discrete PNCs due to their absolute photoluminescence (PL) quantum yield and an observed PL lifetime of 642 ns as well as their good stability in protic solvents. These properties are attributed to synergistic effects among amino, carboxylic and sulfhydryl groups, which not only guide the self-assembly process by cross-linking but also protect the individual PNC from aggregation due to strong binding interactions between the L-cysteine ligands and the NCs. Furthermore, CH3NH3PbBr3 supercrystals have been used in the fabrication of green perovskites and white light-emitting diodes with excellent performance. The facile crosslinking process using unique L-cysteine ligands is promising for rational design and controllable fabrication of functional perovskite-based materials for optoelectronics applications.