Regulation Of Photovoltaic Properties By Grain Boundaries Modification Of Perovskite Films

Perovskite solar cells（PSCs）have attracted extensive attention in recent years due to their advantages such as high energy conversion efficiency,high light absorption coefficient,adjustable band gap and solution-preparation.Although the development of perovskite solar cells is rapid,the defects in perovskite films are still an important factor restricting the improvement of battery energy conversion efficiency（PCE）.Organic-inorganic hybrid perovskite materials are currently the most common optical absorption layer materials used in PSCs,and their narrow band gap structure provides higher current density for PSCs.However,as a polycrystalline material,a large number of grain boundary defects will inevitably occur in the preparation process,which will adversely affect the photovoltaic performance of the device as a non-radiative carrier recombination center in the perovskite layer.In this paper,the organic polymer 502 adhesive and cheap inorganic substances potassium sulfide（K₂S）and copper bromide（Cu Br₂）were introduced into the perovskite grain boundaries by additive engineering.The three common defects from moisture,oxygen,Pb⁰ and I vacancy at the grain boundaries were modified and passivated respectively,which improved the photovoltaic performance and stability of the battery.The main work is as follows:Self-healing perovskite grain boundaries in solar cells via incorporation of 502 adhesive:In this work,502 adhesive used in daily life was introduced into perovskite precursor,using the mechanism of 502 adhesive meeting water to generate self-healing of perovskite grain boundaries in atmospheric environment,blocking the channel of water invading perovskite thin films.At the same time,the morphology of perovskite film is improved by precisely regulating the doping proportion.The PCE of the optimized device is increased from 17.30%to 20.12%,and there is no obvious hysteresis phenomenon.After the addition of 502 adhesive,the device can maintain 95%of the initial efficiency after 1224 h in the atmospheric environment.K₂S passivation of grain boundaries defects to improve the optical stability of perovskite films and device efficiency:In this work,K₂S is used as an additive to modify the grain boundaries of perovskite thin films.The Pb⁰ defects caused by light in perovskite thin films are passivated by S^2-with strong electronegativity.At the same time,Pb S generated by K₂S and excess Pb I₂ is used to further inhibit ion migration at the grain boundaries and increase the number of photogenerated carriers in perovskite thin films.The introduction of K₂S can effectively reduce the defect density of perovskite films and improve the charge transfer efficiency.Through the light aging test of perovskite thin films,it is proved that the addition of K₂S has practical significance for the light stability of perovskite thin films.Finally,we increased the PCE of perovskite battery from 18.57%to 20.47%,which reduced the hysteresis effect and improved the environmental stability of the device.CuBr₂-doped in perovskite grain boundaries to passivate I vacancy defect:In this work,Cu Br₂ was introduced into perovskite film to passivation I vacancy defect at perovskite grain boundary.Through the synergistic action of Cu²⁺and Br^-in perovskite films,the existing Pb²⁺defects are reduced and the formation of new I vacancy defects is inhibited.The introduction of Cu Br₂ can reduce the defects of perovskite thin films in the middle and deep levels,and the proper amount of Cu²⁺can optimize and regulate the surface morphology of perovskite.The optimized device has a higher current density and open circuit voltage,the PCE is increased from 18.53%to20.10%,and the hysteresis of the device is improved.After passivation,the device shows higher stability in atmospheric environment.