| Organic-inorganic hybrid perovskite solar cells（PSCs）have developed rapidly,and their power conversion efficiency（PCE）has increased from 3.8%to 25.6%in just ten years,demon-strating an efficiency comparable to that of silicon-based solar cells.However,the inherent characteristics of organic components in hybrid solar cells seriously reduce the thermal stability of the devices and hinder the commercialization process.On the contrary,all-inorganic perov-skite solar cells with cesium ion（Cs+）substituted can overcome the above thermal stability problems to a certain extent,so researchers began to focus on all-inorganic perovskite solar cells.At present,the efficiency of the cells has exceeded 19%,and the development potential can not be underestimated.Among all types of all-inorganic PSCs,Cs Pb I2Br perovskite has good thermal stability and suitable band gap,and is considered as a photovoltaic material with great application prospect.It has been proved that additives play an important role in the crystallization process of perovskite.In this paper,the polymer polyethylene glycol（PEG）was introduced into the solu-tion of Cs Pb I2Br precursor as an additive.The coordination between Lewis base PEG and lead ions(Pb2+)slows down the crystallization rate of perovskite,regulates the morphology of per-ovskite film,and passivates the defects inside and on the surface of the film.It is found that the energy levels of the Cs Pb I2Br films with PEG are slightly changed,which makes the energy levels match better between the layers,thus reducing the voltage loss at the interface.Finally,the open circuit voltage(Voc)of the device is increased to 1.23 V.By optimizing the condition,the device with PEG obtained a high efficiency of 13.59%,which was nearly 35%higher than that of the control device.In addition,PEG as an organic component protective layer,can ef-fectively prevent water damage to the perovskite film,so the humidity stability of the device is also improved.The type of halogen in the composition of perovskite directly affects the phase stability of perovskite.In this work,a small amount of chloride ion was introduced into the composition of Cs Pb I2Br perovskite,and the efficiency and stability of the cells were improved by optimizing the ratio of halogen ions.It was found that Cl-entered into the lattice of Cs Pb I2Br and replaced some Br-with similar ion radius to regulate the tolerance factor of Cs Pb I2Br perovskite,thus improving the phase stability of Cs Pb I2B perovskite.The optimized Cs Pb I2Br（1-x）Clx all-inor-ganic perovskite solar cell achieves an efficiency of 12.26%and an Voc of 1.25 V.After 500 h in 35%RH environment,the device can still maintain more than 90%of the initial efficiency,demonstrating excellent cell efficiency and stability. |
