Theoretical Exploration Of New Stable Perovskites For Solar Energy Conversion

Currently,photovoltaic and photocatalysis are the two most important ways of solar energy conversion,and the key to develop them lies in the study of functional materials.In recent years,with the rapid development of hybrid perovskite CH3NH3PbI3 in the field of solar energy absorbing materials,the application of perovskite in the field of photovoltaic and photocatalysis have drawn tremendous interest.Since the flexibility of perovskite structure and the diversity of its chemical composition,the members of the perovskite family are extremely large.It is one of the major challenges to find out the functional materials quickly and accurately from the numerous materials.Here,we systematically studied three representative types of perovskite materials:inorganic halide perovskite,oxide double perovskite and halogen-containing oxide double perovskite using a high-throughput computational approach,aiming at finding stable and efficient photovoltaic or photocatalytic candidate materials.Firstly,we systematically studied inorganic halide perovskite ABX3(A=Cs;B=Mg,Ca,Sr,Ba,Zn,Cd,Hg,Ge,Sn,Pb;X=Cl,Br,I).By calculating their decomposition energy,bandgap and optical properties,and CsCdBr3 were selected as the candidate material for solar cells except CsPbI3.CsCdBr3 is beyond the lone-pair s electrons,it has a suitable bandgap(about 1.9 eV),and it has optical properties superior to GaAs and comparable to CsPbI3.It is a stable and efficient solar energy absorbing material.Secondly,we systematically studied 2,018 kinds of oxide double perovskite A2B’B"O6.By considering a tolerance factor(t)-octahedral factor(μ)phase diagram,the scope of study focuses on two types of perovskite,A21+B4+B6+O6 and A22+B2+B6+O6,with a total of 138 candidate materials.Subsequently,the decomposition energy(thermodynamic stability)of 138 candidates withFm3m,P21/c,and R3c phases were calculated using first-principles calculations method.21 stable perovskites were predicted,and 14 among them have never been reported.Verification with existing experimental results demonstrates that the prediction accuracy for perovskite formability is approximately 90%.The predicted oxide double perovskites exhibit quasi-direct bandgaps ranging from 0 to 4.4 eV with a significantly small direct-indirect bandgap difference,balanced electron and hole effective masses,and strong optical absorptions.Since their bandgap values are generally large,they are potential candidates for applications in optoelectronics and photocatalysis.Finally,combine the advantages of halide perovskite and oxide perovskite,we systematically screened 408 kinds of halogen-containing oxide double perovskites A2BXO6(X=Cl,Br and I).Since keep higher+7 valence so that there are only two categories oxide double perovskites:A21+B3+XO6(168)and A22+B1+XO6(240).Via empirical structural factors phase diagram(t-u),and 138 candidates were selected.Furthermore,the decomposition energy(thermodynamic stability)of them was calculated using first-principles calculations method.The screening finally predicted the existence of 14 stable perovskites,and 11 among them have never been reported.Ba2AgIO6 and Sr2AgIO6 were found to be good solar cell materials by the analysis of electronic structure and optical properties.Sr2AgIO6 is new perovskite material that has never been reported,and its electronic structure and optical properties are superior to Ba2AgIO6 which has been discovered.Sr2AgIO6 has not only the high stability of oxide perovskite,but also the superior electronic and optical properties of halide perovskite.As a result,Sr2AgIO6 was selected as an excellent candidate for photovoltaic applications.The discovery of these new materials not only enlarged the variety of perovskite,but also provided more possibilities for experiments.This paper provides an effective new route to explore novel functional materials of perovskite through the study of high-throughput calculation and screening.