Research On The Efficiency And Stability Of 2D And 2D/3D Heterojunction Perovskite Solar Cells

To achieve green and sustainable development,it is deemed necessary to continue to promote and develop clean energy technologies,such as photovoltaics.The new generation of photovoltaic technologies,such as perovskite solar cells,have the characteristics of low-cost,light weight,and simple manufacturing,which are more suitable for the requirements of future development.Perovskite materials are direct bandgap semiconductors with adjustable bandgap,which have lower exciton binding energy,longer carrier lifetime and diffusion length,and higher defect tolerance.The current maximum efficiency has exceeded 25%.However,the inherent instability of the material and sensitivity to environmental factors,such as water,heat,oxygen,and ultraviolet light,have become the primary problems limiting its further development.Layered two-dimensional(2D)perovskite materials are more stable than their three-dimensional(3D)counterpart owing to the presence of organic spacer cations,so preparing of 2D or 2D/3D heterojunction solar cells have been common strategies to improve the stability of devices.In this paper,the distribution and orientation of quantum wells formed by spacer cations,as well as the arrangement of the spacer cation,in these two systems are studied.The specific contents are as follows:(1)By mixing two different organic spacer cations,butanediamine ion(BDA²⁺)and phenethylamine ion(PEA⁺),the 2D perovskite films with concentrated quantum well distribution,vertical orientation and low defect density are obtained.The device based 2D perovskite films with mixed spacer cations achieves an efficiency of 17.21%(open circuit voltage is 0.99 V,short circuit current density is 21.64 m A cm^-2,fill factor is 80.19%).The presence of two different organic cations makes the films and devices display better resistance to moisture and heat.The unencapsulated devices maintain the initial efficiency of over 95%or 75%after being stored in the ambient air of 40±5%relative humidity for500 h or in the nitrogen at 60 ^oC for 100 h.(2)When p-fluorophenethylamine acetate(FPEAAc)is used to modify the interface of3D perovskite,due to its low melting point and volatility,the formed 2D perovskite layer is thin and dense.The modified device achieves a high efficiency of 22.22%with improved the open circuit voltage(1.09 V)and fill factor(80.01%),which is attributed to the defects on the surface are effectively passivated.FPEA⁺ions are anchored on the surface of the perovskite,so the hydrophobic functional groups extend to the outside,which significantly improves the stability of the films and the devices.The FPEAAc modified devices without encapsulated maintained 87.87%of initial efficiency after 500 h at room temperature and40-60%relative humidity,or 90.85%of initial value under the conditions of 85 ^oC and 20-40%relative humidity for 100 h.