【作者】 张鹏；

【导师】 刘伟生；

【作者基本信息】 兰州大学 ， 化学·无机化学， 2025， 博士

【摘要】 长余辉材料凭借自身独特的能量储存和释放机制,在夜间示踪、信息储存、光学防伪和生物成像等领域被广泛应用。目前,常见的硫化物基、硅酸盐基和铝酸盐基等长余辉基质材料通常采用高温固相法进行制备,高温反应对设备参数要求高,能源消耗大,并且制备过程中难以精确调控材料的微观结构和化学组成,极大制约了长余辉材料的实际应用和大规模产业化。无铅钙钛矿材料因其较为温和的合成条件,丰富的组分结构、优异的光学性质和较高的缺陷容忍度,同时避免了铅基钙钛矿结构不稳定性和发光峰位置难以调控的问题,成为一种潜在的长余辉发光材料。然而,现有报道的无铅钙钛矿长余辉材料的光学性能并不理想,表现在激发方式单一、荧光和余辉颜色难以调控、余辉机理不明确等。针对上述问题,本论文开展了多种无铅钙钛矿长余辉材料的构建,通过离子掺杂和有机分子替代策略有效调控了晶体结构和电子陷阱分布,实现了多激发方式下可调谐的多色荧光和余辉,并揭示了余辉陷阱来源和可能的余辉机理过程。基于无铅钙钛矿长余辉材料优异的光学性质,进行了多模态防伪加密、白光LED照明和闪烁体成像的应用研究。具体研究内容如下:（1）利用溶剂热法制备了一系列Sb³⁺掺杂的CsCdCl₃钙钛矿长余辉晶体,通过异价离子取代策略诱导晶格畸变、晶面的择优取向和晶胞形成能的差异,实现了CsCdCl₃由六方相到立方相的精确相调控。六方相CsCdCl₃具有500 nm绿光和700 nm红光的双自陷态发射。随着Sb³⁺掺杂浓度的提高,荧光逐渐转变为单一的绿色自陷态发射。热释光谱测试和缺陷态理论计算证实两相CsCdCl₃均存在适合余辉发光的电子陷阱。由于发光中心和电子陷阱分布的差异,CsCdCl₃相调控过程中伴随着余辉颜色由红色到绿色的转变,特别是CsCdCl₃:0.6%Sb³⁺在经过不同波长的紫外激发后呈现出多色余辉。基于材料荧光和余辉发光颜色的可调性,成功将其应用于高级别防伪加密领域。（2）为了进一步优化CsCdCl₃钙钛矿晶体的长余辉性能,通过Mn²⁺离子共掺杂策略,引入新的发光中心,有效抑制了CsCdCl₃:Mn²⁺/M(M=In³⁺、Sb³⁺和Bi³⁺)非辐射跃迁过程,实现了X射线激发下材料高强度的黄色荧光和余辉。光物理研究表明立方相CsCdCl₃:In³⁺/Mn²⁺具有双重能量传输通道,自陷态能级和Mn²⁺离子之间存在能量传递过程。此外,Mn²⁺离子掺杂调控了电子陷阱分布,陷阱深度主要分布在0.72-0.78 e V之间,余辉持续时间达到10 h。基于CsCdCl₃:In³⁺/Mn²⁺优异的X射线荧光和余辉性能,制备的柔性X射线探测器具有较低X射线检测限,高空间分辨率和延迟成像功能。（3）针对镉基钙钛矿晶体余辉颜色单一且静态变化的难题,采用A位点有机分子替代策略,制备了一系列Sb³⁺离子掺杂的二维层状（C₆H₈N）₂Cd Cl₄有机无机杂化钙钛矿单晶。Sb³⁺离子和有机胺分子的引入,实现了黄色自陷态发射和超长持续时间的蓝色磷光。结合八面体中Cd²⁺离子的短暂红色磷光,在激发光源关闭前后,（C₆H₈N）₂Cd Cl₄:Sb³⁺呈现出时间依赖的动态黄色荧光到红色余辉,再到蓝色余辉的发光颜色变化过程。同时,Sb³⁺离子有效调控了激子辐射复合过程,促进了有机和无机组分之间的能量转移过程,提高了红色磷光的发射效率。基于（C₆H₈N）₂Cd Cl₄:Sb³⁺高量子效率荧光和动态多色余辉发光过程,成功将其应用于白光LED照明和高级别防伪加密领域。（4）镉基钙钛矿晶体受限于掺杂位点和晶体场环境影响,激发源种类和发光模式相对单一。采用Ag⁺和In³⁺共取代Cd²⁺策略制备了一系列Na⁺、Mn²⁺和Er³⁺掺杂的Cs₂Ag In Cl₆无铅双钙钛矿晶体。在紫外（254 nm和365 nm）、近红外（980nm）激发和机械力刺激下,Cs₂Ag_0.8Na_0.2In Cl₆:Mn²⁺/Er³⁺实现了多色荧光、上转换发光、余辉发光和机械发光的多模态光学特性。此外,由于自陷态能级与Mn²⁺离子之间的能量传递过程受到外界温度影响,在77-297 K之间实现了绿色到红色可调的荧光颜色变化。光物理表征和理论计算证明了Mn²⁺和Na⁺掺杂有效调控了电子局域环境,红色余辉发光主要由载流子持续从V_Cl和Na_i形成的电子陷阱逃逸到Mn²⁺发射中心所致。这种集成的多模态发光材料为多功能光学材料和器件的发展提供了新的方向。更多还原

【Abstract】 Long-afterglow materials have found extensive applications in nocturnal tracing,information storage,optical anti-counterfeiting and bioimaging due to their unique energy storage and release mechanisms.At present,conventional long-afterglow matrix materials（such as sulfide,silicate,and aluminate）are prepared by high temperature solid phase method.The high-temperature reaction requires strict equipment parameters and large energy consumption.Moreover,it is difficult to precisely control the microstructure and chemical composition of the crystals during the preparation process,which greatly limits their practical applications and industrialization.Lead-free perovskite has become a potential long-afterglow material because of mild synthesis conditions,rich composition,excellent optical properties and high defect tolerance,while avoiding the toxicity hazards and structural instability of lead-based perovskite.However,the reported lead-free long-afterglow perovskite still suffer from unsatisfactory optical properties,including limited excitation modes,challenging color tunability of afterglow and unclear afterglow mechanisms.To address these issues,this paper systematically constructs various lead-free long-afterglow perovskite through ions co-doping and organic molecule substitution.These approaches effectively modulate the crystal structure and electronic trap distributions,enabling tunable multicolor luminescence and afterglow under multiple excitation modes,revealing the trap origins and underlying afterglow mechanisms.Based on their excellent optical properties,the applications are demonstrated in multimodal anti-counterfeiting encryption,white LED lighting and scintillator imaging.The detailed researches are as follows:（1）A series of Sb³⁺-doped CsCdCl₃ perovskite long-afterglow crystals were synthesized via solvothermal method.The heterovalent substitution strategy induces lattice distortion,strong crystal plane orientation and differences in unit cell formation energy,achieving precise phase control of CsCdCl₃ from hexagonal to cubic phases.PL spectroscopy revealed that hexagonal CsCdCl₃ exhibited dual self-trapped state emissions at 500 nm and 700 nm.With increasing Sb³⁺doping concentration,the luminescence emission gradually transforms into a single green self-trapped state emission.Thermoluminescence spectroscopy measurements and defect state theoretical calculations confirmed suitable electron traps for afterglow emission in hexagonal and cubic phases.Due to the differences in luminescence center and electron trap,the afterglow color of CsCdCl₃ changed from red to green.Notably,CsCdCl₃:0.6%Sb³⁺demonstrated multicolor afterglow upon UV excitation at different wavelengths.Based on the tunable luminescence colors and multicolor afterglow,it was successfully applied in high-level anti-counterfeiting encryption.（2）To further optimize the long-afterglow performance of cubic CsCdCl₃,Mn²⁺ ions co-doping strategy was employed to introduce new luminescent centers and suppress non-radiative transitions in CsCdCl₃:Mn²⁺/M(M=In³⁺,Sb³⁺,Bi³⁺),enabling yellow luminescence and afterglow under X-ray excitation.Photophysical studies revealed that cubic CsCdCl₃:In³⁺/Mn²⁺exhibits dual energy transfer channels,and the energy transfer occurred between self-trapped state and Mn²⁺ions levels.Meanwhile,Mn²⁺doping modulated the electron trap distributions,achieving that trap depths mainly distributed between 0.72-0.78 e V and afterglow duration reached 10 h.Based on the X-ray luminescence and afterglow properties of CsCdCl₃:In³⁺/Mn²⁺,a flexible X-ray detector was fabricated,demonstrating low X-ray detection limit,high spatial resolution and delayed imaging capabilities.（3）To address the challenges of monochromatic and static afterglow colors in cadmium-based perovskite crystals,an A-site organic molecule substitution strategy was employed to synthesize a series of Sb³⁺-doped 2D（C₆H₈N）₂Cd Cl₄ organic-inorganic hybrid perovskite single crystals.The introduction of Sb³⁺ions and organic amine molecules enabled yellow self-trapped state emission and ultralong-duration blue phosphorescence.Coupled with transient red phosphorescence from Cd²⁺ions in octahedrons,（C₆H₈N）₂Cd Cl₄:Sb³⁺exhibited time-dependent dynamic color changes from yellow luminescence to red afterglow and finally to blue afterglow before and after excitation light termination.Meanwhile,Sb³⁺ions effectively modulate exciton radiative recombination processes,promoting energy transfer from organic to inorganic components and enhancing red phosphorescence emission.Based on its high quantum efficiency and dynamic multicolor afterglow properties,（C₆H₈N）₂CdCl₄:Sb³⁺was successfully applied in white LED lighting and high-level anti-counterfeiting encryption.（4）Cadmium-based perovskite crystals are restricted by doping site limitations and crystal field environments,resulting in relatively single excitation sources and luminescence modes.A series of Na⁺,Mn²⁺and Er³⁺-doped Cs₂Ag In Cl₆ lead-free double perovskite crystals were synthesized via Ag⁺/In³⁺co-substitution for Cd²⁺ions.Under ultraviolet（254 nm and 365 nm）,near-infrared（980 nm）excitation and mechanical force stimulation,Cs₂Ag_0.8Na_0.2In Cl₆:Mn²⁺/Er³⁺demonstrateed multicolor luminescence,upconversion emission,afterglow and mechanoluminescence.Additionally,due to temperature-dependent energy transfer process between self-trapped state levels and Mn²⁺ions,tunable green-to-red emission color changes were achieved between 77-297 K.Photophysical measurements and theoretical calculations confirmed that Mn²⁺and Na⁺doping effectively modulated the electronic localization environment.Red afterglow primarily originated from continuous carrier escape from electron traps to Mn²⁺emission centers.This integrated multimodal luminescent material provides a novel direction for the development of multifunctional optical materials and devices.更多还原