| With the rapid development of new generation of information technology such as 5G and artificial intelligence,the feature size of semiconductors is continuously shrinking.Concurrently,the performance of traditional 3D semiconductors and device manufacturing technology have reached a plateau.Therefore,exploring new semiconductor materials with high performance and low power consumption has undoubtedly attracted the interest of researchers.2D sulfide semiconductors（TMDs）,represented by Mo S2,have emerged as promising candidates for achieving high-performance opto-electronic devices due to their layer-dependent bandgap,atomically flat interface and excellent electric field regulation.However,the reduction of dimensions also brings a series of problems.On the one hand,2D TMDs belong to typical interface materials,which are incompatible with the doping technology of traditional 3D bulk materials.On the other hand,atomically thin thickness results in weak absorptivity for TMDs（<10%）,which seriously limits the light responsivity in devices.In addition,owing to thermal strain and local variations in the concentrations of precursors,defects are inevitably introduced in TMDs,at which carriers are easily trapped and decay non-radiatively.Consequently,the fluorescence quantum yield（PL QY）falls to the range of 0.1%to 6%,further restricting the practical application.Therefore,how to improve the light-harvesting of TMDs and significantly enhance their PL QY are important scientific issues that need to be tackled urgently.In this dissertation,by forming hybrid nanostructures with a series of 0D semiconductors or organic molecules,the opto-electronic properties of TMDs（Mo S2,WS2）can be effectively manipulated via charge transfer doping and defect reparation strategy.The specific studies are as follows:（1）Based on carbon dots（CDs）or zinc oxide nanodots（ZDs）,different type II heterostructures are constructed with monolayer Mo S2.Driven by energy band difference of heterostructure,charge transfer doping behavior occurs.Through the injection or extraction of electrons at the interface,the charged trions with relatively low fluorescence efficiency and neutral excitons can be transformed into each other to achieve PL quenching or enhancement in Mo S2.Changing the surface coverage of CDs or ZDs can precisely regulate carrier doping levels,and the electron concentration in Mo S2 can be tunable from 1012 to 1014 cm-2.（2）Based on Cd Se quantum dots（QDs）,type II heterostructure is constructed with monolayer WS2.The fluorescence intensity of WS2 is increased by～2-fold via Cd Se QDs triggered photogenerated carrier gain mechanism.Given the complementarity of these two materials in opto-electronic applications,a photodetector based on 2D/0D heterostructure is constructed via spin-coating process.Combined strong light-harvesting of Cd Se QDs with high mobility of WS2,the hybrid heterostructure exhibits ultrafast response time（～60μs）and improved photodetector performance.（3）A novel organic strong acid methanesulfonic acid（MSA）is exploited to treat monolayer TMDs,and relatively high PL QYs of 10.9%and 32.1%are achieved in Mo S2 and WS2,respectively.Combined with various spectroscopic characterizations such as Raman,UPS,XPS,etc.,the corresponding PL enhancement mechanism is mainly attributed to the synergistic effect of MSA induced p-type doping and sulfur vacancy reparation.According to DFT calculation,the optimal adsorption model is that the specific O atom of MSA is vertically adsorbed above the mono-sulfur vacancy of Mo S2.Furthermore,deformation charge density analysis is used to observe the flow of electrons from Mo S2 to MSA molecules,achieving the p-type doping effect on Mo S2.This study not only enriches the kinds of acids that can improve the luminescent properties of TMDs,but also clearly reveals the mechanism of PL enhancement in this process. |
