过渡金属硫族化合物（transition metal dichalcogenides，TMDs）具有优异的光电性质，在光伏和光催化领域应用前景巨大，受到了广泛关注。然而，TMDs材料介电屏蔽作用弱，光生载流子主要以激子形式存在，限制了这类材料的光电转换效率及光催化效率。TMDs和其它材料构成异质结通常有利于界面电荷分离、延缓电荷弛豫和复合，显著提高了器件的性能。虽然全球范围内有众多课题组利用先进的超快激光技术探测并获得了多种复杂的超快动力学信息，推进了人们对这些光物理过程的理解。但是，理论研究相对匮乏。原因在于理论模拟界面体系的光生非平衡载流子的超快非绝热动力学极具挑战。因此，本文采用组合含时密度泛函理论和非绝热分子动力学，系统地研究了多种TMDs材料与石墨烯（graphene）、金属纳米颗粒和有机分子组成的界面体系的电子转移、弛豫及电子-空穴复合动力学，分析了这些超快过程的影响因素并揭示了深层次的物理机制，加深了人们对实验探测的材料复杂光物理过程的理解，提出了调控载流子动力学的有效策略。创新性成果概述如下：

（1）研究了MoS2/graphene范德华异质结界面电子的正向（electron transfer，ET）和反向转移，发现了界面处形成的内建电场促进了电荷分离，石墨烯上剩余的光生电子以超快的时间尺度注入到MoS2，且不依赖于初始状态能量，电子转移均快于能量损失。尤其当电子弛豫到MoS2的导带边缘时，它会在多个k点之间发生快速的量子跃迁，在2 ps内与留在石墨烯上的空穴发生复合，导致石墨烯狄拉克锥被电子填充，使得MoS2与graphene间的K-K电子-空穴复合（约200 ps）难以发生。模拟获得的正向、反向ET和能量弛豫的时间尺度与实验数据十分吻合。

（2）通过模拟MoS2/graphene横向异质结的界面电子转移动力学，发现非绝热机制主导化学连接的MoS2/graphene的电子转移过程，这种反常现象源于界面处形成的内建电场驱动电子和空穴向相反方向移动，促使电子和空穴分别局域在MoS2和石墨烯子系统，削弱了电子施主和受主间强的C-Mo共价键相互作用。光生电子与MoS2和石墨烯多种声子振动模式耦合，驱使MoS2上的光生电子在180 fs左右转移到石墨烯，而能量损失约为220 fs，说明“热”电子在冷却之前能被成功地提取。

（3）通过对比研究铂纳米颗粒与锡掺杂的铂纳米颗粒敏化的MoS2界面的电子弛豫过程，发现后者显著抑制了MoS2光生“热”电子能量损失过程。进一步分析表明，锡替代掺杂一方面降低了非绝热耦合，另一方面使锡远离铂纳米颗粒基底，产生了远离电子施主态的孤立电子捕获态，它使得MoS2光生电子从纳米粒子态进入到捕获态的过程十分缓慢，被捕获的电子随后在1 ps内弛豫到纳米粒子受主态，导致“热”电子的寿命是未掺杂界面体系的3.5倍以上。该研究为开发高效率、低成本的“热”电子光催化剂提供了有益指导。 

（4）针对有机分子电荷转移掺杂形成的n型和p型TMDs荧光强度增强的起源争议，我们选取MoSe2为研究对象，分别吸附n型和p型掺杂离子与MoSe2形成(MoSe2/RhCp*Cp)+和(MoSe2/SbCl6)-界面，研究掺杂离子效应；通过增减MoSe2两个电子实现n型和p型掺杂，研究电荷效应。通过研究上述四种体系和原始MoSe2的非辐射电子-空穴复合动力学，我们发现：相较于原始体系的电荷复合，(MoSe2/RhCp*Cp)+和(MoSe2/SbCl6)-体系分别延缓和加快了复合，而通过电荷增减获得的n型和p型MoSe2的非辐射复合均被加快。研究结果表明，MoSe2荧光强度增强主要源于掺杂离子及界面相互作用，而非电荷增减。该结果解释了实验中不同分子实现n型和p型掺杂TMDs荧光强度增强和衰减的双重现象，为进一步优化TMDs光电器件性能提供了重要的理论指导。

Transition metal dichalcogenides (TMDs) have attracted widespread attention in the field of photovoltaics and photocatalytic dut to their excellent optoelectric properties. However, photogenerated carriers in TMDs mainly exist as excitons owing to the weak dielectric shielding effect, which limits the photoelectric conversion efficiency and photocatalytic efficiency of such materials. Heterojunctions formed between TMDs and other materials are usually beneficial for charge separation, delaying charge relaxation and recombination at the interfaces, thus significantly improving device performance. Although multiple groups around the world are applying advanced ultrafast laser techniques to detect and obtain a variety of complex ultrafast dynamics information, which has promoted the understanding of these photophysical processes. Nevertheless, theoretical research is relatively limited because it is an extremely challenge for theoretical simulation of the ultrafast non-adiabatic dynamics of photogenerated non-equilibrium carriers in the interfacial systems. Therefore, by using a combination of time-dependent density functional theory (TD-DFT) and non-adiabatic molecular dynamics (NAMD), we have systematically studied the electron transfer (ET), relaxation, and electron-hole recombination dynamics at the interfaces composed of various TMDs materials with graphene, metallic nanoparticles, analyzed the factors affecting those ultrafast processes and established the underlying physical mechanism. The obtained results deepen our understanding of the complex photophysical processes of materials which are experimentally detected, and provide effective strategies to control charge carrier dynamics. The innovative results are briefly summarized as follows:

 (1) By studying the forward and reverse ET at the interface of MoS2/graphene van der Walls (vdW) heterojunction, we found that the built-in electric field formed at the interface promotes charge separation, and the remaining photogenerated electrons on graphene are injected into MoS2 at an ultra-fast time scale, associated with that electron injection is faster than the energy loss regardless of the initial state energy. Upon the electrons relaxing to the edge of the conduction band of MoS2, it undergoes rapid quantum transitions among multiple k points and recombines with the hole left on the graphene within 2 ps. As a consequence, the graphene Dirac cone is fully occupied by electrons and the K-K electron-hole recombination (about 200 ps) is eliminated at the MoS2-graphene interface. The obtained time scales of forward and reverse ET as well as energy relaxation are in good agreement with the available experimental data.

(2) By simulating the interfacial ET dynamics at the MoS2/graphene lateral heterojunction, we found that the non-adiabatic mechanism dominates the injection at the chemically connected MoS2/graphene interface. This anomalous phenomenon aireses from the interfacial built-in electric field formed driving electrons and holes to move to the opposite directions, which weakens the strong C-Mo covalent interaction at the interface by localizing the electrons and holes on the MoS2 and graphene subsystems, respectively. By coupling to multiple phonon vibration modes of MoS2 and graphene, the transfer of photogenerated electrons from MoS2 to graphene takes about 180 fs associated with that the energy loss occurs within about 220 fs, indicating that the "hot" electrons can be successfully extraced before cooling.

(3) By comparing electron relaxation processes between MoS2 sensitized with platinum nanoparticles without and with tin dopant, we observed that the photo-generated "hot" electron energy loss is significantly inhibited in the latter system. Further analysis showed that the replacement platinum with tin not only reduces the non-adiabatic coupling, but also the tin detaces from the base of the platinum nanoparticle, and causes an isolated electron trapping state distant to the electron donor state, which notably slows down the MoS2 photogenerated electrons injection into the electron trap state from the nanoparticle state. Susequently, the trapped electron relaxes to the acceptor state of the tin-doped platinum nanoparticle within 1 ps, leading the lifetime of the "hot" electrons to be 3.5 times longer than that of the undoped interface system. This study provides vaulable guidlines for the development of high-efficiency and low-cost "hot" electronic photocatalysts.

(4) Focusing on the controversy over the origin of the enhanced fluorescence intensity of n-type and p-type TMDs induced by charge transfer doping of organic molecules, we chose MoSe2 as a prototypical system, and investigated the doping ion effect using the (MoSe2/RhCp*Cp)+ and (MoSe2/SbCl6)- interfaces by separately adsorbing an n-type or a p-type doped ion on the MoSe2. Alternatively, we investigated the charge effect using the n-type and p-type MoSe2 obtained by adding or removing two electrons from the MoSe2. By studying the non-radiative electron-hole recombination dynamics of the four systems and the pristine MoSe2 system, compared with that in pristine MoSe2, the charge recombination is suppressed in the (MoSe2/RhCp*Cp)+ but that is accelerated in the (MoSe2/SbCl6)-. In contrast, the electron-hole recombination is persistently accelerated in the n-type and p-type MoSe2 obtained by charge doping. The results show that the enhanced fluorescence intensity of MoSe2 arises primarily from the doping ions and the interaction between interfaces, rather than the charge doping. The results rationalize both the increased and decreased fluorescence intensity in n-type and p-type TMDs doping with different molecules reported experimentally, and provid important theoretical guidelines for further optimizing the performance of TMDs optoelectronic devices.