量子点荧光粉光致生热对LED器件温度场的影响机制研究

With the increase of the lighting comfort requirements, more content, more kinds of phosphors are used to improve the quality of LED light, this undoubtedly increase the weight of the photoexcitation heat generating ratio, which caused the device temperature too high. Quantum dots as one of the nano-scale particles phosphors to improve the light quality, but it has great potential as photoluminescence in the field of lighting and display, photoexcitation heat generating mechanism is more complex which affected the Photoluminescence efficiency. It is necessary to systematically photoexcitation quantum dot phosphors to the LED heat thermal model. First create a composite heat source model, the electron-heating and photoexcitation heating should both be considered. Second make it Compatible between the quantum dot and the silica gel by quantum surface doped. The photoexcitation heat flux with different excitation power and different temperature is carried out by experiment respectively. Third investigate the thermal field distribution variations trends affected by the Seebeck effect of phosphors photo-heating in the LED chip surface and the Peltier effect in the metal-semiconductor interface, respectively. Last establish chip pn-junction, the interface temperature as a function of the quantum dot phosphor coating heat conduction path. It will provide a theoretical model of the photoexcitation heating impact to the temperature field distribution of quantum dot packaged LED device, which will support the theory and technology for quantum dot phosphor used in the photoluminescence application.

随着对照明舒适度要求的提高，更高含量、更多种类的荧光粉被用来改善LED的光品质，这无疑增加了光致生热的权重，造成器件温度过高。量子点作为其中之一的纳米颗粒荧光粉，是未来照明与显示领域不可或缺的光致发光材料，但其光致生热机理更为复杂，影响了光致发光效率，有必要将量子点荧光粉光致生热构建到热学模型中。研究中首先综合考虑LED芯片的电致生热与量子点荧光粉的光致生热，建立LED复合热源模型；然后通过量子点表面杂化修饰手段解决其与有机硅胶的兼容性，降低团聚率，并开展不同激发功率、温度下的量子点荧光粉的光致生热量等实验研究；第三基于塞贝克效应、珀尔贴效应理论研究光致生热对LED芯温度场的影响机制；最后基于以上实验数据及模型，建立芯片pn结、界面处、量子点荧光粉涂覆层热传导路径的温度函数关系，实现量子点荧光粉光致生热对LED器件温度场影响机制的目标，为量子点在光致发光中的应用提供一个热学设计模型。

随着显示技术，尤其是以Micro LED与量子点光致发光相结合的显示技术，显示出了高分辨率、高亮度的优点，已成为热门研究领域。但目前量子点作为光致发光材料，存在热稳定性差的难题，本项目围绕量子点与LED复合热光源模型建模、量子点表面修饰以及热稳定性等方面开展了以下工作：.1、建立了量子点、YAG荧光粉与LED芯片复合热模型：随着荧光粉在光致发光引起热功率的增加，结温呈线性数倍增加。复合光源模型中平均温度与LED单一热源平均温度的关系，亦呈线性倍数关系。另外仿真模拟结果的表面温度与实际红外热像仪测试的表面温度基本吻合。在350mA电流驱动时，结构优化后的器件表面温度比普通结构LED器件低26.5℃。原因是普通结构的LED器件的涂覆方式所引起的量子点重吸收和硅胶热导率低，使得量子点/硅胶层内累积的热量难以扩散所导致。.2、导热薄膜对半导体器件散热性能的改善研究：基于优化制备过渡层的工艺参数，有效解决了DLC与金属基底之间结合力的难题，获得了高导热率的复合薄膜。并且在LED器件、肖特基器件上得到了良好散热的验证。.3、量子点光致发光白光LED器件的制备研究：通过一种简便高效的途径成功合成GQD。将制备的GQD与UV固化硅胶混合，仅需调整GQD/UV膜浓度和厚度即可实现光谱调配。所制备器件具有高达90.3的显色指数。.4、量子点纳米团簇及表面结构修饰的研究：通过使用铜纳米团簇和蓝色QD作为颜色转换层来制备WLED，其显色指数为79.3，CIE色坐标为（0.32，0.33），证明了铜纳米簇作为光致发光材料的优越性能。其次，通过反向微乳化方法对CdZnSeS / ZnS量子点进行了表面改性，并成功地涂覆了二氧化硅壳，修饰后的LED器件在高温，高湿度条件下，显示出相对更好的稳定性。证明了量子点表面修饰可以显著改善量子点作为光致发光材料的热稳定性。.以上研究对量子点在LED领域，尤其是Micro LED光致发光的应用中，对改善量子点发光层的温度、提高热稳定性具有重要的参考意义。