Study On The Optimization Of Inverted Perovskite Solar Cells Based On NiO_x Hole Transport Layer

Since 2009,perovskite materials have shined in the field of perovskite solar cells?PSCs?due to their excellent properties,such as suitable band gap,high absorption coefficient in the visible light range,high carrier mobility,and carrier diffusion Length.As of 2019,the highest certification efficiency is 25.2%,which is close to the highest efficiency of silicon solar cells However,there are still some obstacles in its commercial development,such as stability issues.The p-i-n inverted structure has gradually become a research hotspot because of its small hysteresis effect and low temperature and large area preparation.However,the efficiency of inverted devices reported in actual research is not far from the traditional n-i-p structure.Therefore this paper makes the following studies from the perspective of efficiency and stability:?1?Rare earth ions,due to their partially filled 4f orbitals and vacant 5d orbitals,have rich energy level structures and are widely used in fields such as light emission,display,environmental governance,and photocatalysis.A series of rare earth ions?Ce,Nd,Eu,Tb,Yb?-doped NiO_x hole transport layer?HTL?were prepared using a simple solution method in the study.Characterization results of doped and undoped NiO_x samples and devices show that rare earth ions can effectively regulate quality,conductivity,and work function of NiO_x HTLs have improved device efficiency.Among all the rare earth ion-doped species studied,the best efficiency based on 3%Eu:NiO_x was15.06%,which was an increase of 23.4%compared with undoped?12.20%?.At the same time,under the condition of unpackaged,25-55%relative humidity and 25-35°C temperature range,the device efficiency after 10 days is 97%compared to the original efficiency and the NiO_x device is87%.In this work,it was shown that rare-earth ion doping can be an effective control strategy to obtain efficient and stable inverted perovskite devices.?2?Ionic liquids are a class of compounds composed of organic cationic groups and inorganic anions.They are widely used the field of lithium batteries,catalysts and PSCs due to their advantages such as environment friendly,high ionic conductivity,high temperature and humidity stability,and flexible structure design.Three ionic liquids were used in the study:1-ethyl-3-methylimidazole chloride?EmlmCl?,1-ethyl-3-methylimidazole bromide?EmlmBr?,and 1-ethyl-3-methylimidazole iodide?EmlmI?as modified layer between perovskite active layer and[6,6]-Phenyl-C61-butyric Acid Methyl Ester?PCBM?electron transport layer?ETL?and studied its influence on the efficiency and stability of devices.The results showed that the modification by the three ionic liquids can slightly improve the device efficiency.Among them,EmlmBr has the largest improvement effect,from 15.50%without modification to 17.02%.The stability test results showed that the EmlmBr modified device showed a significant stability improvement compared to the unmodified device.Subsequent analysis shows that the ionic liquid can form a low-dimensional structure with PbI₂.The existence of this structure not only reduces the defect density at the interface of perovskite and PCBM,but also acts as a protective layer to improve the stability of the device.