Interfacial Mechanism Of Organic-inorganic Hybrid Perovskite Solar Cell Materials

Organic-inorganic hybrid perovskite solar cells have received extensive attention due to their high defect tolerance,continuously adjustable direct band gap,and good carrier mobility.At present,their photoelectric conversion efficiency has reached Up 25.5%.However,with the rapid development of conversion efficiency,the problem of device stability has also been exposed,which has become an obstacle to commercialization.In the study of stability,the study of interface mechanism plays an important role in improving the carrier transport performance and enhancing the stability of the interface.In this paper,through the first-principles calculation method based on DFT,the geometric structure,electronic structure,and optical properties of the heterojunction composed of FAPbI₃/SnO₂ are theoretically analyzed,and the interface mechanism is studied.In addition,the photoelectric properties of the rubidium A-doped MAPbI₃/TiO₂ heterojunction interface were studied,and the influence of rubidium doping on the interface structure and the relationship between the structure change and the photoelectric properties were theoretically analyzed.A basic judgment is made about the passivation effect of the mixed interface.The following research results were obtained:The heterojunction interface composed of FAPbI₃ and SnO₂ has been analyzed by differential charge density and average planar potential,and it is found that the FAI interface has more charge transfer than the PbI₂ interface,and the FAI interface may have more bonding than the PbI₂interface;Analysis of the atomic coordinate changes and the distortion of the layered structure after relaxation,the FAI interface structure has a smaller distortion,which is a more ideal interface structure;the calculation results of the interface binding energy of the FAI interface and the PbI₂interface are-0.107e V and-0.087e V,respectively,indicating that the FAI interface structure is a more stable interface structure;the band gaps of the FAI interface and the PbI₂ interface calculated by the HSE06 functional are 1.34e V and 1.21e V respectively;In the analysis of optical properties,the FAI interface has better absorption of visible light and has better charge storage capacity and electrical conductivity.In the FAPbI₃/SnO₂ interface properties,the FAI interface exhibits strong stability.The MAPbI₃/TiO₂ interface uses ten structures doped with rubidium A site and divided by interface type.The analysis of the structure shows that the PbI₂ interface has more Pb-O and Ti-I bonds than the MAI interface,and the interface structure is more stable;the proportion and position of rubidium doping together lead to changes in the interface structure.The MAI interface is more sensitive to the doping of this interface;due to the bonding between the interfaces,the deformation of the PbI₂ frame structure of the first layer close to the interface is smaller than that of the PbI₂frame of the second layer,and the response to rubidium doping is not as significant as that of the second layer;the calculation results of the band structure clearly show the adjustment effect of rubidium doping on the band gap,when 0.125b doping is not considered,as the proportion of rubidium doping increases,the MAI interface shows an increase in the band gap,and the PbI₂interface has a reduced band gap and fluctuates around 1e V;The relationship between optical properties and structure is very obvious,the 0.25 doped MAI interface exhibits strong light absorption in the visible light range as a whole.Rubidium doping has a greater impact on the interface structure of the MAI interface than the PbI₂ interface,which can effectively adjust the band gap and improve the optical properties.In this paper,the structure and properties of the specific interface have been calculated and analyzed theoretically,which is a preliminary exploration of the interface mechanism.There is still a lot of work to be done in the development of perovskite devices,and the unremitting efforts of more researchers are needed to achieve the final commercialization.