| Recently,with the increasing demand of energy sources in society,exploiting novel energy sources and acquire technologies are two significant approaches to gradually reduce the propotion of traditional non-renewable energy in the energy mix.Optoelectronic materials can directly exhibit the conversion between the solar energy and electrical energy by effectively extracting photo-generated carriers in the materials.In recent years,the development of novel high-performance optoelectronic materials and devices has become a research hotspot,which has attracted worldwide attention.However,for a new type of optoelectronic material,there are numerous problems presented in the entire research and development process need to be solved.And the nature of a variety of contained crystalline defects is a key factor affecting the material stability,carrier transport and concentration,as well as the final conversion efficiency of the device.In our work,we firstly introduce our self-developed high-throughput defect property calculating program.Then we take two important types of optoelectronic semiconductors(including photovoltaic materials and p-type transparent conducting oxides)that urgently need to break through the performance bottleneck in the optoelectronic field as aimed materials.On the basis of the program and the firstprinciple calculations,we make related researches on the defect physics in semiconductors through our self-developed high-throughput processing program.The researches have obtained the following innovative results:1.Developing the scripting program for defect property analysis based on firstprinciple calculations.Currently,theoretical studies based on the density functional theory have made strides in predicting the physical properties of defects in materials,including defect formation energy,transition energy levels,and defect concentration under equilibrium state.However,the increase of chemical compositions and structural complexity will correspondingly lead to the exponential increase of the amounts of calculation tasks and data to be processed.Thus,based on the self-developed highthroughput material calculation package,we independently make scripting programs for defect property calculation and data processing based on Python code.This program can construct supercell structures containing different types of defects for threedimensional materials according to the chemical composition and structural information of the host,and carry out the calculation of the formation energy and transition energy level of each defect with different charge states.Then,energy correction,data extraction,results analysis,and data visualization can also be realized by this program.Therefore,this study on the nature of defects carried out by large-scale batch methods can significantly improve the computational efficiency of related research.2.Revealing the physical properties of intrinsic defects in indium-and bismuthbased halide double perovskites and their effects on the electrical conductivity of materials.Halide double perovskites designed based on the “cation transmutation”method have been considered as promising alternatives to lead-based halide perovskites in the field of optoelectronic materials.By calculating the formation energies and transition energy levels of intrinsic defects in Cs2 Ag In Cl6 and Cs2 Ag Bi X6(X=Cl,Br),we found that the silver vacancy is a dominant shallow-level acceptor,while the substitution of indium or bismuth cation on silver cation will introduce deep levels within the band gap,acting as a carrier trap.Furthermore,we found that the position of Fermi level and the unwanted carrier traps can be effectively controlled and suppressed by changing the chemical condition of materials.Thus,the ideal growth conditions to grow p-type Cs2 Ag In Cl6 and Cs2 Ag Bi Cl6 are revealed.3.Investigating the factor affecting the carrier concentration and the effect of impurities on the conductivity in the barium disilicide.Experimental results have demonstrated that the carrier concentration of undoped barium disilicide was as high as~1016-1018 cm-3.This phenomenon was attributed to internal silicon vacancy in experiments.However,theoretical calculations showed that the silicon vacancy would introduce the deep level within the band gap,indicating its limitation to contribute to the carrier concentration.Then,we found the hydrogen interstitial possessed lower formation energy and shallower transition level.Since the hydrogen impurity is difficult to avoid during the synthetic process,this unintentional doping is probably the main cause of the high carrier concentration in the barium disilicide.Furthermore,we also studied the effect of several extrinsic impurities,which have been utilized experimentally,and reveal their existing forms in the barium disilicide.4.Studying the feasibility of tin-containing phosphates utilized as p-type transparent conducting oxides.Previous works have demonstrated the wide band gaps(> 3 e V),good stability and reasonable hole effective masses in tin-containing phosphates(Snn P2O5+n).In this work,we selected Sn3P2O8 and Sn5P2O10,as well as Sn O as a counterpart,to investigate the physical properties of intrinsic defects and hydrogen-related impurities.We found that the tin vacancy and tin interstitial dominantly affected the carrier concentration and type in the tin-containing phosphates.And the ionization energy of the tin vacancy will decrease as the value of n increases.At the same time,hydrogen doping cannot benefit to the p-type conductivity,indicating the requirement to avoid its incorporation during the synthetic process.Furthermore,we proposed a band-edge bonding model of tin-containing phosphates by analyzing their charge densities.On this basis,we obtained a rational explanation for the regular changes in tin vacancy.Our findings suggest that Snn P2O5+n with a higher n would allow for a promising p-type transparent conducting oxide,thus calling further research in this field. |
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