Interface Optimization And Device Performance Of Mixed Ion Perovskite Solar Cells

Organic-inorganic perovskite solar cells(PSCs)have attracted much attention due to their excellent optoelectronic properties and the rapid development of device efficiency.PSCs have undergone continuous optimization and development,which make their certified photoelectric conversion efficiency increases to 25.2%.In addition,perovskite materials have bright application prospects in light-emitting diodes,detectors,memories,etc..Although perovskite materials have many advantages in the field of optoelectronics,the defects of perovskite and the carrier combination at the interface restrict the efficiency development of PSCs.Furthermore,the stability of PSCs is one of the key issues for its commercial application.This paper takes interface engineering and structural engineering as the main methods to promote the efficiency of PSCs and further improve the stability of the device.The main research contents of the paper are as follows:(1)We prepared MAPbI₃/Cs MAFA hetero-structure through surface treatment of Cs MAFA perovskite films with MAI and generated different phases of MAPbI₃ by controlling the reaction temperature.It is interesting to find that different phases of MAPbI₃ play different roles on the efficiency of PSCs.The?-MAPbI₃/Cs MAFA heterojunction formed after annealing at 100?.This structure is beneficial to the separation and transport of holes.In addition,the absorption and EQE of perovskite have been enhanced,which promote the improvement of short-circuit current density.The efficiency of the device increased from 17.8%to 19.75%.However,?-MAPbI₃,which formed at the room temperature,can't promote the efficiency of PSCs.We found that?-MAPbI₃ can't promote the light absorption compared to?-MAPbI₃.In addition,?-MAPbI₃ also fails to promote hole separation.(2)2D PEA₂PbI₄perovskite was introduced to passivate the defects on the surface of Cs MAFA.After annealing the Cs MAFA film treated with PEAI,2D PEA₂PbI₄ perovskite forms on the surface of Cs MAFA by generation with excess PbI₂.The 2D PEA₂PbI₄ can reduce the defects in perovskite,and thus reduce the carrier combination at the interface.The open circuit voltage and fill factor of the device are improved because of the reduction of the defect states density.In addition,2D PEA₂PbI₄ can enhance the hydrophobicity of the perovskite film and improve the stability of the PSCs.(3)The?-MAPbI₃/Cs MAFA heterojunction promotes the device efficiency mainly by improving the short-circuit current,and 2D PEA₂PbI₄ has a significant promotion effect on the open circuit voltage and FF of the devices.Therefore,we prepared a mixed passivation layer of 2D PEA₂PbI₄-3D MAPbI₃,which not only improves the carrier separation and transport at the interface,but also reduces defects and suppresses the non-radiative recombination.The short-circuit current,open-circuit voltage,fill factor and stability of PSCs are greatly improved.Finally,a device with an open voltage of 1.22 V and efficiency of 20.80%has been prepared.The efficiency of PSCs maintains more than 85%of the initial efficiency after 60 days storage.