Influence Of Carbon Quantum Dots Doping On The Efficiency Of Perovskite Films And Solar Cells Prepared By Anti-solvent Method

Since the 21st century,the energy crisis has gradually become a major crisis and challenge for all mankind.People need to seek an environmentally friendly,pollution-free and sustainable energy source.The development and utilization of solar energy has met this demand,and solar cells have also been greatly developed.Perovskite solar cells have received extensive attention in the scientific community in recent years due to their rapid growth in efficiency.Organic-inorganic hybrid perovskite solar cells?herein referred to as perovskite cells?are third-generation all-solid-state thin-film batteries.The highest certified photoelectric conversion efficiency is 24.2%,which has become one of the hot research directions in the field of new solar cells.In this thesis,a two-component green anti-solvent was used to prepare a perovskite film,and a suitable anti-solvent combination and its ratio were obtained.On the basis of this,carbon quantum dots were added to the anti-solvent to realize the doping of perovskite film.The effect of the film on the crystallinity and surface defects was obtained.The doping amount of the device with the best efficiency was obtained.Finally,we used the carbon quantum dots to dope the PCBM electron transport layer.The effects of different additions on the photoelectric conversion performance and stability of the device were systematically investigated.The paper mainly carried out the following three aspects of research:1?A reverse structure?FTO/PEDOT/Perovskite/PCBM/Ag?perovskite cell was prepared using an improved mixed anti-solvent method.The effects of different components and ratio anti-solvents on the crystal growth behavior and optical properties of perovskite films were systematically investigated.It was found through comparison that when chlorobenzene was used as an anti-solvent,pores appeared on the surface of the perovskite film.And accompanied by excessive PbI₂ production,resulting in a decrease in film properties.By using an anti-solvent mixed with ethyl acetate and isopropyl alcohol,the above situation is effectively improved,and the generation rate of photo-generated carriers is greatly improved by using a mixed anti-solvent,and at the same time,the carrier recombination at the interface of the film is obtained.It has also been effectively suppressed.The results of the transient photocurrent also show that the film prepared using the mixed anti-solvent has fewer defects,so the recombination probability of the carriers becomes smaller,so that the interface of the perovskite can be passed faster to the electrode.By measuring the photoelectric conversion efficiency of the device,the efficiency of the device using the mixed anti-solvent was increased from 9.7%to 16.6%compared to the device using chlorobenzene as the anti-solvent.This opens up a new path for the future preparation of high-efficiency perovskite solar cells using green environmental protection processes.2?The effect of carbon quantum dots doped perovskite film on the performance of FTO/PEDOT/Perovskite/PCBM/Ag solar cell devices was investigated.Scanning electron microscopy and X-ray diffraction tests show that the doping of appropriate carbon quantum dots can increase the size of the perovskite film grains and improve its crystallinity and crystal quality.The light absorption test shows that the doped perovskite film is in the visible region.The increase of light absorption,the results of steady state and transient photoluminescence show that the probability of carrier non-radiation recombination decreases,and the defect state density of perovskite film is studied by space charge limiting current quantification,compared with undoped 1.86×10¹⁶cm^-3,the sample after doping decreased to 6.65×10¹⁵ cm^-3,indicating that the incorporation of carbon quantum dots effectively inactivated the film defects,which is consistent with the results of steady-state photoluminescence and transient photoluminescence.The photoelectric conversion efficiency test of the device shows that the doping amount of carbon quantum dots will affect the efficiency of the battery.Excessive quantum dots will become the recombination center of carriers,and too few quantum dots can not effectively reduce the density of defect states,resulting in carriers.Excessive recombination,the device efficiency can reach 18%under the optimal doping amount.Stability testing of the device showed that the efficiency of seven days of storage in the glove box was 91.1%of the initial efficiency.3?The effect of carbon quantum dot doped electron transport layer on the performance of FTO/PEDOT/Perovskite/PCBM:CQDs/Ag perovskite solar cells was investigated.The effect of carbon quantum dot doping on the physical properties of PCBM films was systematically investigated.It was proved that the doping of carbon quantum dots can improve the conductivity of PCBM.It is proved by transient photocurrent and transient photovoltage that the addition of carbon quantum dots can effectively reduce the composite behavior of carriers between the electron transport layer and the perovskite layer,accelerate the transport of carriers between interfaces,and simultaneously UV.The photoelectron spectroscopy test also shows that the incorporation of carbon dots can change the energy level of PCBM,revealing the inherent reason for the more efficient carrier transfer.The device efficiency can reach 18.1%.Carbon quantum dot doping effectively prevents the decomposition of the methylamine lead iodine film,so the stability of the device is significantly improved compared with the undoped device,and the efficiency is improved by 70%under the same aging conditions,which also provides ideas for the preparation of efficient and stable devices in the future.