偶极子发光体在晶体硅表面的自发辐射和近场能量转移特性研究

Hybrid optoelectronic devices based on energy transfer join the merit of optical materials with strong absorption probability and the merit of electronic materials with good carrier transport via near field energy transfer, and bear substantial potential for practical applications. Dipole emitters such as metal nano-particles, quantum dots and fluorescent molecules have strong absorption probabilities of light, and could transfer their excitonic energy to proximal semiconductors such as crystalline silicon. The near field radiation of dipole emitters has large wavenumber components, which could provide the momentum needed to promote interband electron transitions. So the absorption rate of near field radiation should be faster than the far field counterpart. This project intends to study the dependence of the fluorescent properties (fluorescent intensity and lifetime) of an organic fluorescent molecule deposited as a Langmuir-Blodgett monolayer near the surface of crystalline silicon on the molecule-silicon separation (controlled by atomic layer deposition) and the energy of phonons inside silicon. Based on this project, we would elucidate the mechanism of the absorption of near field radiation of dipole emitters by indirect bandgap semiconductors, and this could provide theoretical support to the design and optimization of optoelectronic devices based on dipole emitters and indirect bandgap semiconductors.

基于能量转移机制的复合光电子器件，把吸光能力强的光学材料和载流子传输性能好的电子材料通过近场能量转移结合在一起，具有较好的应用前景。金属纳米粒子、量子点或荧光分子等偶极子发光体具有强的吸光能力，能够将其激发态能量通过近场能量转移传递到电学性能优异的晶体硅材料中。由于偶极子发光体的近场辐射中含有较大波矢的分量，这些近场辐射能够提供带间电子跃迁所需要的动量，因而晶体硅材料对偶极子近场辐射的吸收比对远场辐射的吸收有更快的速率。本项目拟从实验和理论上，研究掺杂有荧光分子的单分子层Langmuir-Blodgett薄膜在晶体硅表面的荧光特性（荧光强度和荧光寿命）与荧光分子和晶体硅的距离（由原子层薄膜沉积方法控制），以及晶体硅中声子能量的关系。通过对本项目的研究，有望阐明晶体硅材料对偶极子发光体发射的近场辐射的吸收机制，并为基于偶极子发光体和间接带隙半导体材料的光电子器件的设计和优化提供理论支撑。

基于能量转移机制的复合光电子器件，把吸光能力强的光学材料和载流子传输性能好的电子材料通过近场能量转移结合在一起，具有较好的应用前景。金属纳米粒子、量子点或荧光分子等偶极子发光体具有强的吸光能力，能够将其激发态能量通过近场能量转移传递到电学性能优异的晶体硅材料中。由于偶极子发光体的近场辐射中含有较大波矢的分量，这些近场辐射能够提供带间电子跃迁所需要的动量，因而晶体硅材料对偶极子近场辐射的吸收比对远场辐射的吸收有更快的速率。本项目从实验和理论上，研究了掺杂有荧光分子的单分子层Langmuir-Blodgett薄膜在晶体硅表面的荧光特性（荧光强度和荧光寿命）与荧光分子和晶体硅的距离（由原子层薄膜沉积方法控制），以及晶体硅中声子能量的关系。研究结果表面，在距离为0~10nm范围内，近场的能量转移作用占主导作用，荧光分子的激发态能量主要通过近场的无辐射能量转移到晶体硅中，通过对比理论计算和实验测试结果表面，温度越低荧光分子向晶体硅的能量转移速率越慢，这说明起主导作用的能量转移机制是声子辅助的带间跃迁过程。