Phosphor converted white light-emitting diodes (pc-WLEDs) are an alternative choice for general lighting due to their superior features such as high efficiency, durability and reliability. However, most pc-WLEDs in the market suffer from problems resulting from the lack of red emission, which can be resolved by adding red-emitting phosphors. The currently dominant red-emitting phosphors are Eu2+-doped nitrides, but the requirement of elevated temperature during synthesis makes them costly, and moreover the over broad emission may result in loss of lumen efficiency. Recently, transition metal Mn4+ doped materials showing very narrow red emission have attracted tremendous interest for compositions based on abundant resources and mild production processes, resulting in a highly efficient way to obtain phosphors with favorable luminescence properties. In this work, we describe the recent progress on transition metal Mn4+-doped inorganic luminescent materials, including oxides (subdivision into alkaline-earth germanates, arsenates, aluminates, titanates, pyrosilicates, phosphates, zirconates, gallates, simple oxides and others), fluorides and nitrides. More specifically, the review focuses on Mn4+ activated red-emitting phosphors that can be effectively excited by NUV and blue LED chips. The excitation and emission spectra as well as the preparation process of some representative phosphors are given and discussed. Meanwhile, the merits and drawbacks of several kinds of matrix materials in applications for white LEDs, as well as some problems, development trends and application prospects in this field of Mn4+ doped phosphors are summarized.

Research progress and application prospects of transition metal Mn4+-activated luminescent materials

Optical temperature sensing of up-conversion luminescent materials: Fundamentals and progress

Bulk glass ceramics containing Yb3+/Er3+: β-NaGdF4 nanocrystals: Phase-separation-controlled crystallization, optical spectroscopy and upconverted temperature sensing behavior

Rare earth (RE) doped phosphors and their emerging applications: A review

Carbon-based quantum dots (CQDs), including spherical carbon dots and graphene quantum dots, are an emerging class of photoluminescent (PL) materials with unique properties. Great progress has been made in the design and fabrication of high-performance CQDs, however, the challenge of developing solid-state PL CQDs have aroused great interest among researchers. A clear PL mechanism is the basis for the development of high-performance solid-state CQDs for light emission and is also a prerequisite for the realization of multiple practical applications. However, the extremely complex structure of a CQD greatly limits the understanding of the solid-state PL mechanism of CQDs. So far, a variety of models have been proposed to explain the PL of solid-state CQDs, but they have not been unified. This review summarizes the current understanding of the solid-state PL of solid-state CQDs from the perspective of energy band theory and electronic transitions. In addition, the common strategies for realizing solid-state PL in CQDs are also summarized. Furthermore, the applications of CQDs in the fields of light-emitting devices, anti-counterfeiting, fingerprint detection, etc., are proposed. Finally, a brief outlook is given, highlighting current problems, and directions for development of solid-state PL of CQDs.

Carbon-Based Quantum Dots with Solid-State Photoluminescent: Mechanism, Implementation, and Application.

Sb3+/Mn2+ co-doped phosphate glasses were prepared by high temperature melting method. The absorption, excitation, and emission spectra of the glasses were investigated. The glasses are transparent in the visible light region and can emit strong red light under 275, 360, 415, or 520 nm excitation. Under 275 nm excitation, the emission colors of the glasses can vary from blue to red with the increasing of Mn2+ ion concentration. The materials will be helpful in developing glass greenhouse for the green plants.

Turning ultraviolet-green into red light in transparent phosphate glasses for greenhouses

A series of phosphate glasses doped with Mn2+/Eu3+ ions were prepared by high temperature melting method to explore reddish orange luminescent materials for greenhouse. The absorption, emission, and excitation spectra of the samples were studied in detail. A wide excitation band at 300-550 nm in the Mn2+/Eu3+ co-doped phosphate glasses was observed. Under the illumination of sunlight, the Mn2+/Eu3+ co-doped phosphate glasses can emit strong red emission. Our materials will be helpful to improve the utilization of solar for glass greenhouses.

Highly efficient reddish orange emission in Mn2+/Eu3+ co-doped phosphate glasses for greenhouse

A biological nano-thermometer based on ratiometric luminescent Er3+/Yb3+-codoped NaGd(WO4)2 nanocrystals

Research on up- and down-conversion emissions of Er3+/Yb3+ co-doped phosphate glass ceramic

Simultaneous tunable fluorescence lifetime and upconversion luminescence enhancement of NaLuF4:Er3+/Yb3+ microcrystals through heavily doped KF for multiplexing

Chengguo Ming

Papers

Turning ultraviolet-green into red light in transparent phosphate glasses for greenhouses

Highly efficient reddish orange emission in Mn2+/Eu3+ co-doped phosphate glasses for greenhouse

A biological nano-thermometer based on ratiometric luminescent Er3+/Yb3+-codoped NaGd(WO4)2 nanocrystals

Research on up- and down-conversion emissions of Er3+/Yb3+ co-doped phosphate glass ceramic

Simultaneous tunable fluorescence lifetime and upconversion luminescence enhancement of NaLuF4:Er3+/Yb3+ microcrystals through heavily doped KF for multiplexing