Study On The Performance Of N-I-P Perovskite Solar Cells Based On Interface Regulation Strategy

Currently,the highest certified power conversion efficiency（PCE）of single-junction perovskite solar cells（PSCs）has reached 25.7%,which is comparable to the traditional commercial silicon solar cells.In the field of photovoltaic technology,the"golden triangle"factors of efficiency,cost,and stability are commonly used to determine the commercial feasibility of solar cells.For PSCs,efficiency and stability are the most noteworthy concern issues among these three elements.The SnO₂,a commonly used electron transport layer（ETL）in PSCs,has some inherent defects that can decrease the electrical performance of ETL,resulting in energy-level mismatch between the absorption layer and ETL,which seriously affects charge-carrier transport and decreases device efficiency.In addition,perovskite materials will also produce many defects at the bulk and interface during low-temperature processing.Moreover,the defects of the perovskite layer are very sensitive to water and oxygen,which are the main way for external corrosion of perovskite films and can affect the stability of the device.Therefore,passivating the defects of ETL and perovskite layer bulk and corresponding interface is the only way for advancing the commercialization of PSCs.Based on this,this paper aims to obtain efficient and stable PSCs,in view of the defect problems in the bulk and interface of SnO₂ and perovskite,as well as the stability problems of PSCs,a variety of strategies such as synergistic passivation and surface modification are adopted.Through the study of the corresponding functional layer and interface characteristics,the influence on the photovoltaic performance and stability of PSCs is clarified,and the mechanism of passivating defect and improving performance is revealed.Finally,the synchronous improvement of the photovoltaic performance and stability of PSCs was realized.The main research contents and results are as follows:1.The black phosphorus quantum dots（BPQDs）and 3-aminopropyltriethoxysilane-modified BPQDs（BPQDs@APTES）were added to SnO₂ and perovskite layers,respectively,to construct double-layer synergistically optimized PSCs.By utilizing high-mobility BPQDs,the surface defects of SnO₂ are filled,which improves the electrical properties of SnO₂.In addition,a series of characterization tests has shown that BPQDs@APTES can regulate the growth of perovskite layer,passivate defects,and improve charge-carrier transport.Moreover,the moisture resistance of perovskite films is improved owing to the hydrophobic properties of APTES.Finally,the efficiency of PSCs is improved to 22.85%.The device also achieves good stability;it can maintain 88%and 62%of the initial efficiency after 30 days under the atmospheric environment and 65±5%humidity conditions,respectively.2.Through the optimization and design of the surface functional groups of Nb₂CT_{x（x=OH,O）}MXene material,according to their corresponding energy-level,Nb₂CT_OH and Nb₂CT_O nanosheets were placed at the SnO₂/perovskite and perovskite/Spiro-OMe TAD interface,respectively.The high-mobility Nb₂CT_xnanosheets improves the charge extraction and transport at the corresponding interface,and regulates interface energy-level arrangement.In addition,the double-interface modification strategy also improves the crystal quality of perovskite layer.The electrical simulation and experimental data further show that the Nb₂CT_O nanosheets located at the grain boundary of the perovskite film significantly increases the hole current density at the interface and realizes the charge-carrier transport balance in the device.Finally,in double-interface modified devices,the open circuit voltage(V_OC)significantly increased to 1.253 V,the fill factor（FF）increased to 81.07%,and the PCE increased to 24.11%,which is the highest efficiency to date for PSCs based on MXene material.In addition,the unencapsulated optimized device also shows excellent long-term stability.3.Ionic liquid is introduced at the SnO₂/three-dimensional（3D）perovskite interface to form one-dimensional（1D）/3D composite perovskite structure.Anion in ionic liquid can improve the surface defects of SnO₂ and regulate the electrical properties of the interface;the vertical PbI₂ gradient distribution in the perovskite film is realized by the interaction between the cation and the excess PbI₂at the bottom interface.The crystallization,defect state density and charge carrier dynamics of the perovskite film were further characterized and analyzed,revealing the working mechanism of the PbI₂ regulation strategy for improving device performance.This method also inhibits the photodegradation of perovskite layer caused by excess PbI₂.Finally,the efficiency of the optimized devices is increased to 23.61%,V_OC,short-circuit current density(J_SC)and FF reached 1.250 V,23.70 mA/cm² and 79.71%,respectively.Moreover,the light stability of the device has also been significantly improved.4.Since the research work in the previous section did not endow the perovskite film with hydrophobic properties,in this work,superhydrophobic dyes cis-Ru（H₂dcbpy）（dnbpy）（NCS）₂（Z907）were further used for internal encapsulation（IE）of perovskite films.Through the interaction between the C=O in the Z907 molecule and the uncoordinated Pb²⁺,reduces the surface defects of the perovskite layer.Moreover,the superhydrophobic alkyl chain in the Z907 can effectively block the erosion of water and thermal on the perovskite film,and inhibit the Pb leakage and ion migration in the device.Finally,the device exhibits an impressive PCE of 24.28%,V_OC of 1.253 V,and FF of 81.25%.The PCE and V_OC are the highest values based on 1.60 e V bandgap perovskite absorption layer device.In addition,the device also shows excellent humidity and thermal stability.