| As a renewable clean energy,solar energy has very important practical significance in dealing with the current depletion of fossil energy and the environmental pollution caused by its use.Solar cells are an effective way to solve the energy crisis and environmental pollution by using solar energy.In recent years,perovskite materials have been widely used in solar cells,photodevices,memories,photocatalysis and other fields due to their ad-justable band gaps,high optical absorption coefficients,small effective mass of carriers and high carrier mobility.At the same time,the optimiza-tion and improvement of its performance have also attracted great attention of researchers.After more than a decade of development,the power con-version efficiency(PCE)of perovskite solar cells have increased rapidly from 3.8%to 25.7%.Although perovskite materials have become the ob-ject of extensive research in the scientific research field,most of the per-ovskite photovoltaic devices currently prepared contain toxic element,i.e.,lead,which causes serious environmental pollution and greatly limits its applications in actual production and life.Therefore,looking for clean and efficient lead-free perovskite solar cell materials has become a research hotspot in recent years.In addition,the counterpart of perovskite,anti-per-ovskite has attracted the scientific interest of the majority of researchers because of its similar structural characteristics and physical properties to perovskite.In this paper,based on density functional theory,the first-prin-ciples calculation method was used to study the electronic structure and optoelectronic properties of the AZr X3(A=Ba,Ca;X=S,Se,Te)lead-free perovskite,the needle-like?phase AZr X3(A=Ca,Sr,Ba;X=S,Se)lead-free chalcogenide perovskites,and X4A2O(X=Ca,Sr,Ba;A=As,Sb,Bi)anti-perovskites.The main research contents and conclusions are summarized as fol-lows:We investigated the photoelectric properties of AZrX3(A=Ba,Ca;X=S,Se,Te)lead-free perovskite.The results indicate that all AZr X3 lead-free perovskites are direct band gap semiconductor materials.The toler-ance factor of the materials is between 0.85 and 0.95,the formation energy is between-1.09 and-1.83 e V/atom,and the decomposition energy is be-tween-0.09 and 0.06 e V/atom,indicating that AZr X3 perovskite has a sta-ble crystal structure.The band gaps of Ba Zr S3 and Ca Zr S3 were calculated using the hybrid density functional(HSE06)calculation method and con-sidering the spin-orbit coupling(SOC)effect.The calculated results are very close to the experimental measurements,indicating that the theoretical research is highly reliable.BaZrS3 has the characteristics of small hole ef-fective mass(0.21 m0),high carrier mobility,wide visible light absorption range,high light absorption coefficient(?4×10~5 cm-1),and spectral limit maximum efficiency(SLME)up to 32.36%,higher than MAPb I3(MA=CH3NH3)(?30%),indicating that Ba Zr S3 is a promising solar cell material.The calculation of optoelectronic properties of AZr Se3 and AZr Te3 show that they are also potential photoelectric materials.All these indicate that AZr X3 perovskite is a photoelectric material with excellent physical properties.The electronic structure and optical properties of the needle-like?phase AZr X3(A=Ca,Sr,Ba;X=S,Se)lead-free chalcogenide perovskite have been calculated by first-principles calculations based on density func-tional theory.The calculations have shown that the tolerance factors of these materials are in the stable range of perovskite.The calculated elastic constants meet the Bonn-Huang criterion,indicating that these materials have good mechanical stability.Further molecular dynamics(AIMD)sim-ulations have shown that the thermodynamic properties of needle-like?phase AZr X3 lead-free chalcogenide perovskite are stable.According to the band structures,needle-like?phase AZr X3 perovskite materials are all di-rect band gap semiconductors.The electron effective mass of needle-like?-Sr Zr S3 is 0.30 m0,and a light absorption coefficient of?4×10~5 cm-1 in the visible region,indicating that it has good visible light absorption ca-pacity.When the thickness of the material is 1.0?m,SLME is up to?32.64%,indicating that it is a potential solar cell absorber material.At the same time,the calculation of the photoelectric properties of AZr Se3 shown that they are also potential photoelectric materials.X4A2O(X=Ca,Sr,Ba;A=As,Sb,Bi)anti-perovskite are direct semi-conductor materials,which contains heavy elements.HSE06+SOC calcu-lation method is used to calculate the band structures.It is concluded that X4A2O anti-perovskite have a good band gap regulation range(0.59-1.90e V).The elastic constants and AIMD calculation results have shown that its have mechanical stability and thermodynamic stability.At the same time,the highest carrier mobility is 729.84 cm~2V-1s-1,the highest optical absorp-tion coefficient is 6.5×10~5 cm-1,and the simulated SLME are close to 30%.These calculations have shown that X4A2O have excellent photoelectric properties.It can be predicted that X4A2O anti-perovskite have great po-tential applications in solar cells and photodetectors. |
PDF Full Text Request