Study On The Preparation Of Highly Efficient And Non-Hysteretic Perovskite Solar Cells Based On Two-Step Method

In recent years,organic-inorganic hybrid perovskite solar cells（PSCs）have attracted the attention of many researchers because of their simple device structure,low preparation cost and high photoelectric conversion efficiency.Since 2009,the power conversion efficiency（PCE）of perovskite solar cells has increased from 3.8%to 24.2%,approaching the commercialized silicon solar cells.Right now,PSCs have become the fastest developing technology in the field of photovoltaic and showed a huge potential commercial value.However,in order to realize the commercialization and popularization of perovskite solar cells,it is necessary to improve the PCE and stability of perovskite solar cells.The highly efficient devices require not only scientific device structure,excellent transport layer（electron transport layer and hole transport layer）and favorable interface,but also the high quality perovskite film.In this paper,high quality perovskite thin films were prepared by controlling the film-forming conditions during the preparation of perovskite films,and the effective control of crystal growth process was realized,and on the basis of that,the quality of perovskite thin films was improved.The photoelectric performance of hole transport layer is improved by additive engineering.Finally,the PCE of perovskite solar cells is greatly improved,which provides a new way to improve the efficiency of perovskite solar cells.This paper mainly completed the following two aspects of research work:Regulation of the quality and properties of perovskite light absorption layer films.The perovskite thin film is very sensitive to the film forming conditions,such as annealing temperature and time,the composition and concentration of precursor solution,spin coating rate and solvent selection will affect the final morphology of the film.Therefore,based on the two-step spin-coating method,we optimized the film formation in three aspects:precursor solution spin-coating rate,annealing temperature and annealing time.Finally,the perovskite thin films with high quality and excellent optical and electrical properties have been successfully prepared,and the corresponding solar cell devices have achieved a PCE as high as 18.0%.The improvement of the hole transport layer performance and the passivation of the interface.Efficient perovskite solar cell devices usually use 2,2′,7,7′-tetrakis-（N,N-di-p-methoxyphenyl-amine）9,9′-spirobifluorene（spiro-OMeTAD）as the hole transport layer material.At present,the highest as PCE of using spiro-OMeTAD as hole transport layer is 22.3%.However,the large number of holes in the hole transport layer seriously limits the improvement of device photovoltaic performance.Based on this,we creatively used the TBP?xPbI₂ formed by PbI₂ and TBP instead of TBP to add to the hole transport layer.Scanning electron microscope,electrochemical workstation,time-resolved fluorescence spectrometer,solar simulator and other instruments and equipment are used to test and characterize the hole transport layer and device.The results show that the addition of PbI₂can not only restrain the hole formation and increase the hole mobility,but also passivate the interface between perovskite active layer and hole transport layer,which reduce the recombination of carriers on the interface.The transport and extraction of carriers are promoted,and the photovoltaic performance of the device is greatly improved.The PCE of solar cell devices is increased from 17.6%to 20.3%and the hysteresis is eliminated.In the meanwhile,the response time of the device to light is accelerated,in which the response time of the unadded device is 26s,while the device added is less than 1s.In summary,we successfully prepared high-quality perovskite thin films by controlling the growth process and crystal quality of perovskite crystals.By using cheap additives to optimize the hole transport layer and passivate the interface,the performance of the hole transport layer is improved,the interface between perovskite and hole transport layer is passivated,and the photovoltaic performance of the device is greatly improved.In short,our work provides a new way to improve the PCE of perovskite solar cells.