Green Preparation Of Antimonene Quantum Sheets And Their Applications In Organic Optoelectronic Devices

Organic optoelectronic devices have attracted widespread attention in recent years due to their properties of low-cost,flexibility,and large-scale fabrication et al.However,compared with silicon-based and perovskite optoelectronic devices,the efficiency of organic optoelectronic devices is still relatively lower.The inefficiency of organic optoelectronic devices is mainly due to low carrier mobility and limited exciton dissociation ability of organic active materials.Currently,optimizing device structure by inserting an interface modification layer and modifying the active materials by doping a suitable narrow band gap two dimensional（2D）materials with high carrier mobility are the useful strategies to effectively improve the weak charge transport,exciton dissociation and light absorption of the device.Among the reported 2D optoelectronic materials,antimonene shows stable structure,suitable band gap（about 1.0 e V）,excellent electrical and optical properties,which are conducive to improve the capability of charge transport and exciton dissociation of organic optoelectronic devices.Up to now,a green and efficient method for preparing antimonene and regulating its morphology/structure is urgently needed.Herein,this dissertation mainly focuses on the green fabrication of antimonene and its applications in organic optoelectronic devices.Firstly,a green and efficient method is found to fabricate well-dispersed antimonene quantum sheets（AMQSs）.Then,AMQSs are used to promote the performance of organic solar cells（OSCs）and organic light emitting diodes（OLEDs）,and the related mechanisms are further explored,respectively.Finally,the nonlinear optical properties of AMQSs are characterized by an open aperture Z-Scan technology.The main results of this dissertation are as follows:（1）Antimonene with different sizes are fabricated by ultrasonication-assisted liquid phase exfoliation in different solvents.The results show that atomically thin AMQSs with uniform size（≈2.2 nm）can be fabricated from the bulk by using ultrasonication-assisted liquid phase exfoliation in environmentally friendly 1-ethyl-3-methylimidazolium trifluoroacetate.The yield of AMQSs(1.1 mg m L^-1)has been increased by nearly three orders of magnitude compared with previously reported methods,and AMQSs can disperse in both polar and non-polar solvents.The work function of AMQSs film is-4.4 e V,calculated from ultraviolet photoelectron spectroscopy.In addition,the energy band gap structure of AMQSs film is estimated via the absorption spectrum of the AMQSs film,that is,the band gap of AMQSs film is 0.97 e V.（2）In OSCs,AMQSs doping in active materials and modifying the interface between the hole transport layer and the active layer are used to optimize the photovoltaic performance of the devices and the mechanism is explored,respectively.By doping AMQSs in the active layer of PTB7:PC₇₁BM-based OSCs,the power conversion efficiency（PCE）of the optimally doped device is increased to 9.75%.Compared with the reference device,the enhancements on PCE,short-circuit current density(J_sc),and fill factor（FF）of the optimally doped AMQSs device are 25%,16.7%and 8.4%,respectively.The mechanism for the improved performance is that the AMQSs can enhance the light absorption and the exciton dissociation,and reduce the charge recombination of OSCs.Furthermore,high-efficiency OSCs were prepared by using AMQSs to modify the interface between hole extraction layer（HEL,cuprous thiocyanate,Cu SCN）and active layer.In addition,Cu SCN and AMQSs can form an efficient bilayer HEL.For the PTB7-Th:PC₇₁BM-based fullerene OSCs,the bilayer Cu SCN/AMQSs HEL gave rise to a 12%enhancement of PCE compared to that of the reference device with pure Cu SCN HEL.For the PBDB-T-2F:IT-4F-based non-fullerene OSCs,a PCE of 10.14%is obtained in the bilayer device,which is an increase of 10%compared to that of the reference device.Furthermore,OSCs based on bilayer Cu SCN/AMQSs HEL also exhibit superior stability.The main reasons for AMQSs interface modification to improve device performance is that the AMQSs layer can help passivate surface defects of Cu SCN,resulting in diminished recombination loss and depressed exciton quenching effect.（3）The performance of OLEDs has been improved by using AMQSs to regulate the energy level of the hole injection layer（HIL,PEDOT:PSS）,and the mechanism of AMQSs effect on OLEDs performance was explored.As a result,the Ir（ppy）₃-based green OLEDs with PEDOT:PSS:AMQSs as the HIL show a lower turn-on voltage of 3.0 e V（reduced from 3.3 e V to 3.0 e V）and the maximum current efficiency,power efficiency and external quantum efficiency of the optimized AMQSs-doped OLEDs are 14.86%,68.99%and 13.32%higher than these of the reference device,respectively.The remarkable improvements are mainly ascribed to doping AMQSs can effectively adjust the work function of PEDOT:PSS HIL from-5.2 e V to-4.9 e V,which reduced the hole injection barrier and enhanced the hole injection and transport capabilities of HIL.（4）The non-linear optical absorption performance of AMQSs has been explored using the open aperture Z-scan technique.The results show that AMQSs possess excellent optical limiting property under the excitation lasers at wavelengths of 532 nm and 1064 nm,respectively,which indicates that AMQSs show potential in broadband nonlinear optical devices.