基于A3M2(PO4)3型单基质白光材料的结构设计与发光性能研究

White light emitting diode (WLED) is recognized as the fourth generation solid state light source due to the advantages of high efficiency, environmental friendly and long lifetime. Currently, many scientific problems still exist in the combination of WLED, such as in “blue + YAG：Ce3+”, the lack of red component in spectrum results in low color rendering index; In “blue/NUV chip + multi-color phosphor”, the superposition of spectrum in different phosphor causes severe self-absorption. Further, different thermal stability in different hosts can shift the chromatic coordination in high operating temperature of LED. To solve these problems, the project focuses on the single phase white emitting approach. Firstly, series of A3M2(PO4)3 are synthesized by high temperature solid state method. By incorporating different types of activatosr into the exact site of host, the photoluminescence of various activators are studied. Secondly, the energy transfer mechanism is investigated, and the relationship between structure and performance is constructed. Thirdly, the thermal stability is measured, and charge compensation with different valence state ions is proposed to improve the luminous efficiency. Furthermore, the potential application of the single phase WLED is evaluated. We attempts to achieve single phase white LED with high lumen efficiency, high thermal stability and low color shift.

白光LED因在发光效率、节能环保、光稳定性、使用寿命等方面较传统光源有较大优势被誉为第四代光源。目前，白光LED的组合存在很多科学问题，如蓝光芯片+YAG：Ce3+组合缺乏红光成分、芯片+多粉体组合中粉体间不同光谱特性导致自吸收严重、不同粉体热稳定性不同导致在LED工作温度下热猝灭严重或出现色漂移等。为进一步提高LED性能，本项目拟采用高温固相法制备系列A3M2(PO4)3 (A为Li或Na；M为Cr，Fe或Sc)型材料，通过将不同种类的发光中心掺杂进入合适的格位并合理的调节制备气氛和稀土离子浓度来研究不同离子在基质中的发光性能和能量传递机理，建立组成、结构与性能之间联系。测试粉体的热稳定性，并拟通过离子对的交换进行电荷补偿来提升性能，使其在LED工作温度下依然拥有较高的发光效率。最终封装成器件，力争得到高流明效率、高热稳定性、低色漂移的新型单基质白光LED。

主流白光LED中InGaN蓝光芯片发射出的高强度蓝光会对视网膜细胞造成损伤，过多暴露在强蓝光下会抑制褪黑激素的生成也会造成健康问题。近紫外芯片(350-420 nm)激发的白光LED可以避免以上问题。本项目以Na3Sc2(PO4)3和Ca8ZnLu(PO4)7为基质，通过等价取代、异价取代和共掺杂激活离子的方式，调控材料的发光性能，获得了一批适用于近紫外芯片激发暖白光LED的荧光粉。本项目所完成的工作汇总如下：（1）研究了取代或掺杂后晶体结构及掺杂离子在晶体中的格位占据，例如，以β-Ca3(PO4)2为模板对Ca8ZnLu(PO4)7结构精修，并通过第一性原理验证了结构的有效性；（2）研究了结构对发光性能的影响规律，构建了结构-发光性能之间的关系；例如，K+对Na3Sc2(PO4)3:Eu2+部分取代引起Eu2+周围环境的变化，实现了稀土离子Eu2+在固溶体物相中发光性能的精细调控，发光强度也大幅提升。Zn2+对Na3Sc2(PO4)3:Eu2+不等价取代调控缺陷深度和浓度，提升反热猝灭性能。（3）研究Eu2+-Mn2+、Tb3+-Eu3+能量传递，通过调控获得单基质白光材料。（4）将获得的荧光粉制备成器件，探究了其在近紫外白光LED中的潜在应用。例如，Ca8ZnLu(PO4)7:Tb3+无浓度猝灭，425 K时，Ca8ZnTb(PO4)7: 0.2Eu3+发光强度仍为初始强度的87%，展现出优异的热稳定性且仅有微弱的色漂移。将其与BAM: Eu2+蓝粉用370 nm近紫外芯片成功封装成荧光粉转换的暖白光LED器件。将Ca8ZnLu(PO4)7: 0.03Eu2+, 0.20Mn2+与360 nm近紫外芯片封装成显色指数为88.6、相关色温为4842 K的白光器件。项目实施期间，在国际重要学术期刊发表标注项目资助的研究论文7篇；申报国家发明专利4项。本项目圆满完成了任务书中所预定完成的研究成果。