Theoretical Study On Optical Properties Of Doped Double Perovskite Materials

Double perovskite solar cells are currently a hot spot in research due to its simple synthesis methods and excellent properties.Compared to CH₃NH₃PbI₃ perovskite,double perovskite has outstanding characteristics such as non-toxicity and environmental stability and so on.However,the application of double perovskite solar cells is limited by the poor photoelectric conversion efficiency.In order to solve problems,we have studied the double perovskite by means of elements doping replacement.The main contents of this paper are as follows:?1?Based on double perovskite Cs₂AgBiBr₆,we use Sb³⁺and In³⁺,which are similar to the Bi³⁺ionic radius,to dope the Bi³⁺position.Optimized calculations of the doped structure,including structure,electronic properties,and optical properties,were systematically calculated.The results show that Cs2AgBi1-xMxBr6?M=In,Sb?has a more suitable band gap than Cs₂AgBiBr₆.In particular,it is worth mentioning that Cs2AgBi1-xInxBr6 is a direct band gap compound with a significant improvement in optical properties.Our element doping completes the conversion from indirect bandgap to direct bandgap.?2?In order to further explore the influence of element doping on materials at different locations in this paper,the positions of Ag+ and Br-in Cs₂AgBiBr₆ are gradient doped.The elements are the same group elements of the corresponding,Au/Cu and Cl/I.Two different systems were obtained after doping the elements,and their related properties were systematically studied and analyzed.The results show that Cs2Ag1-xMxBiBr6?M=Au,Cu?has a more stable material structure than Cs₂AgBiBr₆,and the band structure exhibits a smaller band gap,which is more in line with the performance requirements of photovoltaic devices for absorbing visible light;Compared with Cs₂AgBiBr₆,Cs₂AgBiBr₆?1-y?X6y?X=Cl,I?system,Cs₂AgBiBr₆?1-y?I6y has better band gap structure and stronger light absorption capacity,Cs₂AgBiBr₆?1-y?Cl6y is excellent in structural stability,but has a certain degree of weakening in optical properties.?3?Based on the above studies,we have doped the Na+ and Sb³⁺ positions of the new substance Cs₂NaSbI₆,and obtained two systems:Cs₂Na_1-xK_xSbI₆ and Cs2NaSb1-xInxI6,which were systematically studied,and obtained excellent results.The structural stability of Cs₂Na_1-xK_xSbI₆ has been improved.The structural stability of Cs2NaSb1-xInxI6 decreases with the increase of In³⁺ doping amount.The two systems Cs₂Na_1-xK_xSbI₆ and Cs2NaSb1-xInxI6 complete the conversion from indirect band gap to direct band gap.Cs2Na1-xKxSbl6 has the same absorption capacity as Cs₂NaSbI₆.The light absorption capacity of Cs2NaSb1-xInxI6 is decreased,but it rises at the long wavelength of visible light.These studies provide new research directions for photovoltaic fields such as dual perovskite solar cells and open up new roads for their development.