Ce^(3+)掺杂Y⁃Si⁃O⁃N体系荧光材料晶体及能带/电子结构对其发光特性的影响

Effect of Crystal and Band/Electronic Structures on Luminescence Property of Ce^(3+) Doped Y-Si-O-N Luminescent Materials

当前白光LED主要通过采用蓝光芯片激发黄色发光YAG∶Ce^(3+)来实现,由于光谱中缺少足够的红光成分,光源通常存在显色性能较差的问题。因此,长波荧光材料(>600 nm)的应用对于高品质白光LED照明的实现尤为重要。为了进一步掌握配位结构对Ce^(3+)能带/电子结构的影响规律,指导Ce^(3+)离子掺杂长波荧光材料的设计研发,本文通过第一性原理计算,利用广义梯度近似(GGA)中密度泛函理论(DFT)深入研究了Y-Si-N-O体系荧光材料Y2Si3N4O3∶Ce^(3+)、Y_(4)Si_(2)N_(2)O_(7)∶Ce^(3+)和Y_(3)Si_(5)N_(9)O∶Ce^(3+)的晶体及能带/电子结构特性,并结合实验测试结果对晶体及能带/电子结构与Ce^(3+)发光特性之间的内在关系进行分析。研究结果表明,针对Ce^(3+)离子掺杂长波荧光材料的设计研发,可以重点对具有高含N量、短Ce—N配位键、低对称性配位结构特性的氧氮化物材料进行筛选。

Currently,the use of a blue LED chip in conjunction with the yellow-emitting YAG∶Ce^(3+) phosphor is recognized as the main approach for achieving high-brightness white light.However,due to the spectrum defect of the long-wavelength component,this approach has resulted in a poor color rendering performance of LED lighting devices.Thus,the luminescent materials with longwavelength emission(>600 nm)are very important for high quality LED lighting devices.In order to develop Ce^(3+) doped luminescent materials with long-wavelength emission,the effect of coordination structure on the band/electronic structures of Ce^(3+) needs to be further studied.In this paper,based on the first-principles calculation,the crystal and band/electronic structures of Y_(2)Si_(3)N_(4)O_(3)∶Ce^(3+),Y_(4)Si_(2)N_(2)O_(7)∶Ce^(3+),and Y_(3)Si_(5)N_(9)O∶Ce^(3+) luminescent materials in Y-Si-O-N system were studied by using the density-functional theory(DFT)of the generalized gradient approximation(GGA).To understand the relationship between band/electronic structures and the luminescence properties of Ce^(3+),the emission and excitation spectra of these luminescent materials were also studied.According to the research conclusions,the oxynitride structures with higher nitrogen content,shorter Ce—N bond lengths,and lower point symmetry coordination structure are suitable for the development of Ce^(3+)doped luminescent materials willing to achieve long-wavelength emission.