Preparation And Characterization Of Carbon-based Hole-transport-layer Free Perovskite Solar Cells In An Atmospheric Environment

Perovskite solar cells（PSCs）have achieved rapid development in recent years,and the highest certified photoelectric conversion efficiency（PCE）has reached 25.6%.In order to solve the problems of high production cost and poor stability of hole transport materials in PSCs,carbon-based hole-transport-layer free PSCs were developed.However,the preparation of PSCs is mostly completed in an oxygen-free and low-humidity glove box.It not only raises the threshold of device fabrication but also makes the preparation process more complicated,which seriously hinders the industrialization process of PSCs.Considering these issues,the main research objective of this paper is to prepare high-efficiency and high-stability carbon-based hole-transport-layer free PSCs in an ambient atmosphere.The specific research content includes three aspects:In order to solve the problem of excessive Pb I₂ residue in the traditional two-step method,this paper used the principle of Pb I₂ dissolution-recrystallization and proposed an improved double two-step method to prepare perovskite films.XRD and SEM test results showed that the perovskite film obtained by this method not only has no Pb I₂ residue but also is dense and uniform;UV-Vis and PL test results confirmed that the device’s light absorption capacity is enhanced and the charge transfer efficiency is improved.The open-circuit voltage(V_oc)of the corresponding device was 0.85 V,the short-circuit current density(J_sc)was 15.56 m A/cm²,the fill factor（FF）was 0.58,and PCE reached 7.58%.It could still maintain 80%of the initial PCE after being stored in a high-humidity atmospheric environment for two weeks.In order to further increase the V_oc of the device,MABr was introduced into the MAI solution to achieve the bromine-doped perovskite film.SEM results showed that a proper amount of bromine doping can improve the crystallization of perovskite,and the obtained perovskite grain size reaches the maximum.The J-V test results showed that when the molar ratio of MAI:MABr is 5:3,the V_oc of the device reached 0.98 V,the J_sc was 13.1 m A/cm²,and the PCE reached the highest 7.8%.In order to improve the hole transport ability of the device,the P-type semiconductor material Ni O_x is mixed with carbon material to prepare carbon electrodes.In addition,to improve the conductivity of Ni O_x particles,the Ni O_x is doped with Li²⁺and Cu²⁺.The J-V test results showed that Cu²⁺doping significantly improves the J_sc of the device from 15.5 m A/cm²to 21.3 m A/cm²,and PCE reaches 8.23%,while Li²⁺doping didn’t improve the performance of the device.Through XPS characterization,it could be found that the ratio of Ni³⁺/Ni²⁺in Cu²⁺doping Ni O_x increased from 1.19:1 to 2.73:1,which shows that the doping of Cu²⁺improves the conductivity of the pristine Ni O_x particles,which is the main reason for the PCE enhancement of the device.