Study On The Passivation And Mechanism Of The Interface Of Ammonium Methoxide Lead Iodide Perovskite Solar Cells

Organic and inorganic perovskite materials have attracted great attention in the field of solar cell applications due to their excellent optical properties.After years of development,the efficiency of perovskite solar cells（PSCs）has made a rapid progress,and a variety types of cells with different structures have been developed,which has great development potential.Planar perovskite solar cell is a common type of cell structure,which has the advantages of simple and flexible manufacturing process,and is suitable for the needs of industrial development.Related reports have been increasing in recent years.However,planar perovskite solar cell also has problems to be solved.The formation process of perovskite film is difficult to control and a large number of interface and crystal defects are easily formed during the crystallization process.In fact,not only do perovskite films suffer from defects,but also low-temperature prepared electron transport layers（ETLs）.These defects can cause serious non-radiation recombination,affect device performance and stability,and hinder the pace of industrialization.In order to solve this problem,this paper adopts the method of interface modification.The common planar orthomorphic perovskite solar cells with Sn O₂/MAPb I₃/Spiro-Me OTAD structure were taken as the research object,different modification materials were selected to modify the device interface by adding modification layers between the electron transport layer and the perovskite layer or between the perovskite layer and the hole transport layer.The overall performance of the device was improved at the same time.It also improves the device stability.Finally,the mechanism of action of each modification material is analyzed and summarized.The main research work is as follow:1.Caesium sulfate（Cs₂SO₄）solution is introduced as a modifier between the electron transport layer and the perovskite layer,which modifies the interface defects and enhances the charge transfer capability between the two interfaces.For the electron transport layer,the addition of Cs₂SO₄ can effectively passivate the defect of the electron transport layer through the interaction with Sn⁴⁺.At the same time,it can make the interface of the electron transport layer more compact and smoother,which is conducive to the subsequent growth of perovskite thin film.For the perovskite layer,cesium ions can diffuse into the perovskite layer during the formation of the perovskite film,passivate the internal defects,and improve the crystallization quality of the perovskite layer.On the other hand,while passivating surface defects,sulfate can form a"bridge"between the electron transport layer and the perovskite layer due to the intense coordination between SO4^2-and Sn²⁺or Pb²⁺,which can improve the carrier transport efficiency.The carrier transport efficiency of Cs₂SO₄ modified perovskite solar cells has been significantly improved,and the device photoelectric conversion efficiency（PCE）has increased from 16.68%to 20.93%.Under ambient conditions of50%-65%relative humidity,the device still maintains 70%of the initial efficiency after350h aging test.This method of surface modification with Cs₂SO₄ solution can improve the performance of PSC simply and effectively,which provides a new idea for the selection of modifiers.2.We used ferrocene dicarboxylic acid（FDA）doped p-type poly（9-vinylcarbazole）（PVK）to modify the perovskite/Spiro-Me OTAD interface,forming a modified layer on the surface of the perovskite layer.In this structure of photovoltaic devices,the carboxyl group（COOH）in FDA can generate strong coordination with lead ions on the surface of the calcium titanium layer,and can also interact with excessive MA⁺and I^-through hydrogen bonds,which can effectively passivate perovskite surface defects.And the N atom in PVK can couple with Pb ions to passivate defects and promote high-quality crystallization of perovskite batteries.In addition,the hydrophobic components of FDA and PVK can also effectively protect the perovskite layer from environmental factors,increasing the stability of perovskite batteries.The PCE of perovskite solar cells with FDA:PVK modification increased from 16.28%to20.67%,after 500 hours of aging test under ambient conditions of 50%-65%relative humidity,the efficiency was still maintained at 78%of initial efficiency after 500h aging test.The method of jointly using antioxidant PVK and FDA to modify the perovskite/HTL interface can improve device performance and stability simply and efficiently,providing a new idea for the selection of modification methods for perovskite solar cells.