Excitons have significant impacts on the properties of semiconductors. They exhibit significantly different properties when a direct semiconductor turns in to an indirect one by doping. Huybrecht variational method is also found to influence the study of exciton ground state energy and ground state binding energy in Al_xGa_1?xAs semiconductor spherical quantum dots. The Al_xGa_1?xAs is considered to be a direct semiconductor at Al concentration below 0.45, and an indirect one at the concentration above 0.45. With regards to the former, the ground state binding energy increases and decreases with Al concentration and eigenfrequency, respectively; however, while the ground state energy increases with Al concentration, it is marginally influenced by eigenfrequency. On the other hand, considering the latter, while the ground state binding energy increases with Al concentration, it decreases with eigenfrequency; nevertheless, the ground state energy increases both with Al concentration and eigenfrequency. Hence, for the better practical performance of the semiconductors, the properties of the excitons are suggested to vary by adjusting Al concentration and eigenfrequency

发光层中载流子的平衡以及拓宽的激子分布对于制备高性能白光有机发光二极管(WOLEDs)至关重要。采用蓝光热激活延迟荧光(TADF)分子DMAC-DPS、绿光磷光分子Ir (ppy)₂(acac)和红光磷光分子RD071制备了基于激基复合物主体的TADF/磷光杂化WOLEDs。在发光层中引入TCTA:DPEPO激基复合物作为主体不仅平衡了电荷和空穴传输，拓宽了激子复合区，并构建蓝-绿-红发光层之间级联式激子能量传递，有效提升了激子利用率，降低了器件的效率滚降。通过调控发光层中载流子平衡及激子分布，白光器件的最大电流效率(CE)、功率效率(PE)和外量子效率(EQE)分别为37.1 cd·A⁻¹、36.4 lm·W⁻¹和17.5%，并且在1000 cd·m⁻²亮度下依旧保持在26.6 cd·A⁻¹、18.2 lm·W⁻¹和12.3%，对应色坐标(CIE)和显色指数(CRI)分别为(0.451,0.428)和88。值得注意的是，在1000~5000 cd·m⁻²亮度范围内，CIE变化仅为(0.006, 0.004)，表现出优异的色稳定性。同时，通过单极性主体和双极性主体的对比，阐明了双极性主体中载流子复合及激子能量传递机制。最终，通过器件传输层的优化进一步降低了器件的工作电压，提升了载流子平衡性，器件EQE及PE分别提升至19.3%和52.6 lm·W⁻¹，并保持了高的显色指数(CRI=90)及良好的色稳定性。

近年来，金属卤化物钙钛矿发光材料由于具有优异的光电性能，被广泛地应用于金属卤化物钙钛矿发光二极管（Perovskite light-emitting diodes, PeLEDs），被视作下一代显示和照明领域的发光光源。激子利用率是影响PeLEDs效率的关键因素之一，研究者采用各种各样的方法将激子限制在钙钛矿发光层中，对激子能量回收利用以提高激子的利用率。文中将概述通过添加剂辅助法、器件界面工程和结构优化法，将传统荧光材料、磷光材料、热激活延迟荧光材料引入器件，改善绿光和蓝光PeLEDs的光电性能方面所做的尝试。并简要地介绍激子限制作用的原理，以及不同类型的发光材料引入PeLEDs中激子的能量转移机理和器件光电性能提升的物理机理。

The collective response of macroscopic quantum states under perturbation is widely used to study quantum correlations and cooperative properties, such as defect-induced quantum vortices in Bose–Einstein condensates and the non-destructive scattering of impurities in superfluids. Superfluorescence (SF), as a collective effect rooted in dipole–dipole cooperation through virtual photon exchange, leads to the macroscopic dipole moment (MDM) in high-density dipole ensembles. However, the perturbation response of the MDM in SF systems remains unknown. Echo-like behavior is observed in a cooperative exciton ensemble under a controllable perturbation, corresponding to an initial collapse followed by a revival of the MDM. Such a dynamic response could refer to a phase transition between the macroscopic coherence regime and the incoherent classical state on a time scale of 10 ps. The echo-like behavior is absent above 100 K due to the instability of MDM in a strongly dephased exciton ensemble. Experimentally, the MDM response to perturbations is shown to be controlled by the amplitude and injection time of the perturbations.

蓝光OLED材料是电致发光领域的关键和难点。基于高能激发态转换的“热激子”材料表现出优异蓝光材料的潜能。本文通过调节给受体的推拉电子能力，以蒽为核心构筑单元、三苯基苯为弱给体、苯氰基为受体，设计合成了一种新型D?π?A结构分子TACN。扭曲的三苯基苯提供了高度扭曲的分子构象，有效减弱了聚集态下的猝灭效应，因此TACN表现出高的荧光量子产率（聚集态下47%）。实验结果和理论分析表明，TACN具备“热激子”特征，其大的T₂?T₁能隙（1.45 eV）有效阻碍了从T₂到T₁的内转换（IC）过程，而小的T₂?S₁能差（0.18 eV，T₂> S₁）有利于促进反向系间窜越（RISC）过程。基于TACN的非掺杂器件表现出深蓝色发射（λ_max= 444 nm），半峰宽（FWHM）为59 nm，色坐标为（0.17，0.13）。其最大外量子效率（EQE_max）为8.3%，相应的激子利用率（EUE）最高为88.7%。

为实现有机光电探测器对三基色（红、绿、蓝）的全响应以及器件性能的改善，研究了在P3HT∶PCBM活性层中，掺入非富勒烯受体ITIC实现光谱拓宽以及通过改善迁移率的平衡性和活性层表面形态，进而改善探测器性能的方法，着重研究了ITIC受体含量对探测器光电学性能的影响。在此基础上，获得了一个覆盖400~800 nm波长范围的三基色探测器，并且在低偏压-1.5 V下三基色（波长为630、530和460 nm）的外量子效率EQE和比探测率D^*分别达到了56%、68%、52%和1.17×10¹² Jones、1.4×10¹² Jones、1.2×10¹² Jones。结果表明：在P3HT：PC₆₁BM中混入适量的ITIC，不仅可将光谱拓宽到400~800 nm，改善器件的光学特性，而且还可以提高激子解离率和载流子收集率，降低混合薄膜中的双分子复合，使器件电学特性得到了明显改善。本文研究为研发宽光谱高探测率三基色有机光电探测器提供了一种新思路。

准二维Ruddlesden?Popper（R?P）卤化物钙钛矿具有优越的光电特性，在太阳能电池、发光二极管、激光器等光电器件中受到广泛关注，但严重影响载流子的弛豫和传输特性的激子?声子之间的相互作用还未得到充分揭示。与广泛研究的三维钙钛矿结构相比，准二维钙钛矿存在天然形成的量子阱结构，具有更大的激子结合能，激子效应更加明显，但对其激子?声子相互作用的研究仍然较少。因此，我们通过溶液法制备了准二维R?P型钙钛矿（PEA）₂Cs_n-1Pb_nBr_3n+1薄膜，其增益系数高达~1 090.62 cm^-1，获得了低阈值（~12.48 μJ/cm²）的放大自发辐射。基于此，我们通过变温荧光光谱（77~300 K）和瞬态吸收光谱技术研究了（PEA）₂Cs_n-1Pb_nBr_3n+1薄膜随温度变化的发光特性，以阐述其内部的激子?声子相互作用对其发光性能的影响。发现在低温域内（77~120 K），由激子?声子相互作用引起的带隙变化相对较弱，晶格热膨胀占主导地位；随着温度升高，激子?声子相互作用对带隙变化产生较大影响。另一方面，激子?声子相互作用会促使发光光谱线宽加宽，但我们在77~120 K的温度范围内观察到了反常线宽变窄现象，这归因于由局域化效应引起的多量子阱中的能量转移机制；直到120 K之后，激子?声子相互作用引起的谱线加宽才足以逆转这一趋势。本文对准二维钙钛矿的激子?声子相互作用的研究对于提高准二维钙钛矿光学性能及其发光应用具有指导价值。

零维有机-无机杂化金属卤化物因可调控的自陷态激子发射在发光和显示等领域具有很好的应用前景。特别是同时具有单线态和三线态激子发射双带光谱的零维金属卤化物在白光固态照明应用中极具潜力。本工作报道了两种零维杂化锑基氯化物（C₂₄H₂₀P）₂SbCl₅（Ⅰ）和（C₂₄H₂₀P）₂SbCl₅?H₂O·0.5DMF（Ⅱ）（C₂₄H₂₀P为四苯基膦，Ph₄P）。在低能量光子（如360 nm）激发下，化合物Ⅰ和Ⅱ分别呈现出由自陷态激子发射的红色和黄色的单峰宽带光谱。此外，当用高能量光子（如310 nm）激发时，Ⅱ的光谱呈现出双带白光发射，除黄光发射带外，还出现了一个源于单线态自陷激发发射的蓝光发射带。研究表明，通过引入和去除DMF和水分子，化合物Ⅰ和Ⅱ能实现可逆转化。该研究揭示了小分子对零维杂化金属卤化物晶体结构的调控机制，从而实现单带发射和双带发射之间的转变，为设计具有小分子传感应用的零维金属卤化物奠定了研究基础。

Colloidal CdSe quantum dots (QDs) are promising materials for solar cells because of their simple preparation process and compatibility with flexible substrates. The QD radiative recombination lifetime has attracted enormous attention as it affects the probability of photogenerated charges leaving the QDs and being collected at the battery electrodes. However, the scaling law for the exciton radiative lifetime in CdSe QDs is still a puzzle. This article presents a novel explanation that reconciles this controversy. Our calculations agree with the experimental measurements of all three divergent trends in a broadened energy window. Further, we proved that the exciton radiative lifetime is a consequence of the thermal average of decays for all thermally accessible exciton states. Each of the contradictory size-dependent patterns reflects this trend in a specific size range. As the optical band gap increases, the radiative lifetime decreases in larger QDs, increases in smaller QDs, and is weakly dependent on size in the intermediate energy region. This study addresses the inconsistencies in the scaling law of the exciton lifetime and gives a unified interpretation over a widened framework. Moreover, it provides valuable guidance for carrier separation in the thin film solar cell of CdSe QDs.Colloidal CdSe quantum dots (QDs) are promising materials for solar cells because of their simple preparation process and compatibility with flexible substrates. The QD radiative recombination lifetime has attracted enormous attention as it affects the probability of photogenerated charges leaving the QDs and being collected at the battery electrodes. However, the scaling law for the exciton radiative lifetime in CdSe QDs is still a puzzle. This article presents a novel explanation that reconciles this controversy. Our calculations agree with the experimental measurements of all three divergent trends in a broadened energy window. Further, we proved that the exciton radiative lifetime is a consequence of the thermal average of decays for all thermally accessible exciton states. Each of the contradictory size-dependent patterns reflects this trend in a specific size range. As the optical band gap increases, the radiative lifetime decreases in larger QDs, increases in smaller QDs, and is weakly dependent on size in the intermediate energy region. This study addresses the inconsistencies in the scaling law of the exciton lifetime and gives a unified interpretation over a widened framework. Moreover, it provides valuable guidance for carrier separation in the thin film solar cell of CdSe QDs.