Effect Of 2-Chloroethylamine Hydrochloride On The Performance Of Inverted Perovskite Solar Cells

In recent years,organic-inorganic hybrid perovskite solar cells（PSCs）have received widespread attention due to their high photoelectric conversion efficiency and simple preparation process.It is critical to improve the performance of the device regarding the selection and optimization of the hole transport layer（HTL）.Nickel oxide（NiO_x）HTL is widely used in PSCs due to its good chemical stability,high hole mobility,and simple preparation method.The stability of three-dimensional（3D）perovskite polycrystals is poor.For example,the widely studied CH₃NH₃Pb I₃ perovskite material,due to the volatile methylamine organic cation（CH₃NH₃⁺）,is easily affected by external environments such as light,heat,water and oxygen,which is not conducive to the long-term stability of the device.Quasi-two-dimensional（2D）perovskite has large organic spacer cations,higher crystal formation energy and a more stable structure,which is expected to solve the problem of poor stability of PSCs based on 3D perovskite.However,PSCs based on quasi-2D perovskite have low photoelectric conversion efficiency due to their low carrier mobility.It is a promising strategy to use a 2D-3D mixed perovskite active layer to effectively block water and oxygen from entering the film,strengthen charge migration and improve device efficiency and stability.In this paper,a two-step method is used to prepare inverted PSCs,with ITO/NiO_x/Perovskite/PCBM/BCP/Ag as standard devices,and the main research work is to improve the efficiency and stability of PSCs,which is divided into the following two parts:（1）Modification of NiO_x and perovskite interface.In the actual preparation of NiO_x,Ni vacancies with high ionization energy are very easy to appear,resulting in a low hole density in NiO_x and low intrinsic conductivity.In addition,due to the mismatch between the Fermi level（E_F）of the perovskite active layer and NiO_x,the energy level shift between the two materials after contact is relatively large,the built-in electric field is weak,and the hole extraction capability is insufficient.In this paper,a ultra-thin insulating polymer layer（PMMA）is inserted between the NiO_x and the perovskite interface as the passivation layer.By choosing the appropriate thickness of PMMA,the photoelectric conversion efficiency（PCE）is increased from 15.57%of the standard device to 16.18%.The optimized device is used as a reference device to carry out the second part of the research work.（2）As an organic amine salt material,ethylamine organic amine salt（CEA）is introduced to form a 2D-3D mixed perovskite layer in the bulk or surface of the perovskite,which can effectively passivate the bulk defects and the interface defects,and reduce the non-radiative recombination.In addition,the hydrophobic CEA can protect the perovskite layer and prevent water vapor from entering the inside of the perovskite active layer.To this end,this section introduces CEA ionic materials into PSCs based on the following two ideas to study its impact on the efficiency and stability of PSCs:using the aforementioned PMMA-optimized inverted planar PSCs as the reference device,（a）using CEA as the interface layers are placed on both sides of the perovskite to study the effect of CEA on the efficiency and stability of the device;（b）CEA is added as a dopant to the perovskite precursor to explore the effect of CEA on the efficiency and stability of the device.When CEA is used as the perovskite upper interface layer,the average PCE of the device reaches 18.03%,the photoelectric conversion efficiency（PCE）of the optimal device based on inverted PSCs is 19.28%,and the open circuit voltage(V_oc)is1.11 V.The current density(J_sc)is 22.46 m A/cm²,and the fill factor（FF）is 0.77.When CEA is doped with Pb I₂,the average PCE of the device is 17.07%,and the PCE of the best device is17.54%,where V_oc is 1.04 V,J_sc is 21.80 m A/cm²,and FF is 0.78.Through the systematic characterization of the aforementioned two optimized devices,it is not difficult to find that the introduction of CEA can form 2D-3D perovskite at the surface interface of the 3D perovskite,which not only helps to improve the crystalline quality of the perovskite film,but also effectively passivates the surface and interface defects of the perovskite,reduces the defect density,inhibits carrier recombination,improves the extraction efficiency of the device,and improves the thermal stability and air stability of the device.This kind of 2D-3D hybrid structure has great potential in the development of high-performance and high-stability PSCs.