Preparation And Performance Optimization Of Perovskite Optoelectronic Devices Based On Additive Engineering

Metal halide perovskite as a new type of organic/inorganic hybrid semiconductor material,with a series of advantages such as high absorption coefficient,long carrier diffusion length,high luminous efficiency and low cost,has received extensive attention in perovskite solar cells?PSC?,perovskite light-emitting diodes?PeLED?and other aspects.Researchers have tried many ways to improve the performance of perovskite optoelectronic devices.The optimization of perovskite films is particularly important.To this end,researchers have done a lot of work,such as improving device structure,optimizing preparation processes,interface engineering,solvent engineering,element doping,additive engineering,and so on.Additive engineering is favored by everyone because of its relatively simple method.Based on the additive engineering,this work analyzes and optimizes the morphology of the perovskite layer and applies it to PSC and PeLED to improve the performance of the perovskite optoelectronic device.It can be divided into the following three parts:?1?PSC performance is improved by adding barium ferrite?BFO?nanostructures to toluene anti-solvent.The flaky and cubic BFO nanostructures were separately dispersed in antisolvent toluene.The surface was rinsed with toluene during spin coating of the MAPbI₃ perovskite precursor.The experimental results show that BFO dispersed in the anti-solvent toluene acts as a carrier for inducing nucleation of perovskite crystals and has a positive effect on the crystallization of perovskites.After rinsing with toluene dispersed with BFO,the morphology of the perovskite film is improved with increased grain size,reduced grain boundary and less surface roughness.This facilitates the transport and collection of carriers,thereby improving the short-circuit current and photoelectric conversion efficiency of the perovskite solar cell device.Among them,the perovskite film washed with toluene containing cubic BFO has the best crystallinity,which lead to the best device performance.Compared with the device obtained by pure toluene washing,the short-circuit current is increased from 18.66mA/cm² to 20.74 mA/cm².As a result,conversion efficiency increased from 13.80%to 15.81%.?2?PSC performance was improved by adding 1,8-diiodooctane?DIO?to the MAPbI₃ perovskite precursor.DIO is used as a common additive in organic solar cells.In recent years there have been reported on its application to perovskite solar cells as well.In this work,DIO is applied in a one-step film fabrication system that does not require an anti-solvent.This method is simple and reproducible.By investigating the effect of volume content of DIO on the performance of PSC,it is concluded that when the volume of DIO is 1%of the total volume of precursor liquid,the crystallization process of perovskite can be slow down.Crystal grains grow along the surface of the substrate to obtain a larger grain size and reduced grain boundary,which increase the short-circuit current of the device from18.3 mA/cm² to 21.33 mA/cm²,resulting in the photoelectric conversion efficiency increased from14.18%to 17.02%.?3?The work of this part firstly explored the effect of MABr and PbBr₂ ratio on MAPbBr₃ film.The MAPbBr₃ film was optimized by adjusting the ratio of them.Then,on the substrate with NiOx and PEDOT:PSS as the hole transport layer,1%DIO was added to the optimal proportion of MAPbBr₃ perovskite precursor solution to further study the effect of DIO on MAPbBr₃ film and PeLED on different substrates.The results show that when the ratio of MABr and PbBr₂ is 2:1,the grain size of MAPbBr₃ becomes smaller,the film is dense and no excess of MABr is precipitated,and the film has the strongest luminescence intensity.In this system,the MAPbBr₃ film prepared by using PEDOT:PSS as the substrate is more compact and has no obvious defects,so PEDOT:PSS is more suitable as a hole transport layer;while the introduction of the additive DIO does not play a positive role in the performance of the PeLED.Compared with the reference device,the brightness of the device decreased slightly after adding DIO,from 5873 cd/m² to 4817 cd/m².And due to the increase of current density,the device current efficiency is dropped from 8.5 cd/A to 6.7 cd/A.