The Study Of Anion And Cation Doping On Performance Of Perovskite Solar Cells

Perovskite solar cell is a kind of photovoltaic cell with great potential at present,whose power conversion efficiency has quickly climbed from 3.8%to 24.2%in less than ten years.However,perovskite solar cell of traditional structure usually needs expensive hole transport materials and noble metal electrodes which requires to be fabricated by vacuum evaporation.While Carbon material is used as electrode in the hole-conductor-free carbon-based perovskite solar cell.This kind of perovskite solar cell costs low and is easy to be fabricated,showing a broad prospect for commercial application.In this paper,we fabricated the carbon-based perovskite solar cells by screen printing.The X-site and A-site of perovskite crystal were doped by introducing different anions and cations in one-step method.We used testing methods such as J-V,XRD,SEM,EDS,UV-vis and PL to investigate the doping effects on performance of carbon-based perovskite solar cells.The chief research contents and conclusions are as follows:Firstly,we adopted the single variable method to optimize the preparation process of the cells.The influences of solvent types,amount of perovskite precursor,heat treatment time,thickness of TiO₂ compact layer and mesoporous layer on device performance were explored to determine the optimum experimental conditions for preparation of MAPbI₃ carbon-based solar cells.When we used DMF as the solvent of precursor solution,with 5?L precursor solution to fabricate devices,15?L/cm² TAA solution to spray the compact layer and the mass ratio of TiO₂ slurry to terpinol to be1:2.25,we can achieve optimal device by annealing at 100 ^oC for 20 minutes.The power conversion efficiency of the optimal device was 8.74%for reverse scan.Secondly,we investigated the influence of introducing different anions?Cl^-,I^-,Br^-?into the precursor solution on performance of MAPbI₃.We firstly introduced MACl with different doping concentrations,fingding that the crystal quality of perovskite and power conversion efficiency of the device increased initially and then decreased when the doping concentration of MACl gradually increased from 0.15 M to 1.05 M.The device doped with 0.45 M MACl showed the best performance with the power conversion efficiency of 14.50%for forward scan and 14.27%for reverse scan,respectively.XRD indicated that the Cl element didn't enter the lattice of perovskite,and EDS indicated that most of Cl elements in the device evaporated in the form of MACl gas after annealing.Combining XRD with J-V test,we can know that the hysteresis of carbon-based cells is not necessarily related to the quality of perovskite crystals.PL test manifested that hysteresis could be alleviated by efficient charge separation at the interface between perovskite and TiO₂.In order to explore whether MA⁺or Cl^-plays the role,we doped MAPbI₃ with MAI and MABr equal to the optimal concentration?0.45 M?of MACl,and the device performance was not improved,which ruled out the possibility of MA⁺acting alone.Thirdly,we replaced MA⁺with FA⁺,Cs⁺or K⁺to study the effects of different cations doping on the properties of MAPbI₃ perovskite based on the above research.Our research showed that appropriate doping amounts of FACl and CsCl could replace ions in the A-site of MAPbI₃,thus affected the crystal structure of perovskite and improved the light absorption performance of perovskite and the life of photogenerated carriers.J-V test indicated that the short-circuit current of the device doped with FACl increased.The device doped with 0.5 M FACl showed excellent performance with the power conversion efficiency of 13.66%for forward scan and 13.43%for reverse scan.J-V test and XRD indicated that the open-circuit voltage and thermal stability of the devices doped with CsCl were improved.The device doped with 0.25 M CsCl showed outstanding performance with the power conversion efficiency of 11.68%for forward scan and 11.71%for reverse scan.A series of tests showed that K⁺failed to replace MA⁺in the lattice of MAPbI₃,so the doping of KCl had no positive effect on the crystallization properties and light absorption properties of MAPbI₃ in the cabon-based structure.