Study On Interface Regulation And Photovoltaic Performance Of All Inorganic CsPbIBr₂ Perovskite Solar Cells

Since 2009,organic-inorganic lead halide perovskite solar cells(PSCs)have made remarkable progress in the photovoltaic field,which has attracted extensive attention of researchers all over the world.At present,the highest power conversion efficiency(PCE)of certified single junction PSCs has reached 25.7%.Among them,the PCE of CsPbIBr₂ based perovskite solar cells has rapidly increased from 4.7%in2016 to 11.08%,making it a potential photovoltaic device.In addition,CsPbIBr₂based perovskite solar cells have become one of the research hotspots in the field of perovskite solar cells because of their stable chemical structure and excellent theoretical photoelectric performance.However,the traditional preparation process of CsPbIBr₂ is not perfect,resulting in problems such as small grain size,uneven film formation and many defects in the film,which makes carrier transmission difficult and greatly affects the performance and stability of photovoltaic devices.To solve the above problems,in this thesis,high-quality CsPbIBr₂ thin films were prepared by one-step method.At the same time,s-benzylisothiourea hydrochloride(SBTCl)was used to passivate the surface defects of Perovskite Thin Films,and then CsPbIBr₂ light absorbing layer with no pinholes and high crystallinity was obtained.Although it is effective to change the quality of perovskite films by surface passivation,it is difficult to fundamentally solve the deep defects in the process of perovskite film formation.Therefore,the crystallization of CsPbIBr₂ was induced by controlling the temperature of CsPbIBr₂ precursor solution,and large-size CsPbIBr₂ thin films were prepared,which further improved the efficiency of photovoltaic devices.The main research contents and results are as follows:(1)A multifunctional organic molecule s-benzylisothiourea hydrochloride(SBTCl)was used to passivate the surface of all inorganic CsPbIBr₂ perovskite films.Using the coordination between the electronic groups of SBTCl and defects,the density of defect states and the surface work function are significantly reduced,and more hole carriers are extracted and transferred.After SBTCl concentration optimization,the open circuit voltage of all inorganic CsPbIBr₂ perovskite battery device was increased to 1.327 V,and the PCE was as high as 10.56%.In addition,due to the high hydrophobic property of SBTCl passivator,it can effectively prevent surface water from penetrating into perovskite films.The efficiency of the prepared battery devices can still be maintained above 90%after being stored at 5%relative humidity(RH)for more than 110 days without packaging,and the stability under50%RH and continuous illumination has also been greatly improved.(2)By adjusting the temperature of precursor solution,the film quality of CsPbIBr₂ perovskite film is improved,so as to improve the performance of battery devices.By adjusting the temperature of the precursor,the size of 1?m stable microcrystals can be formed first in the solution,which can induce the directional nucleation and crystallization of perovskite.The grain size of the finally prepared CsPbIBr₂perovskite thin film increases,and the film defects are greatly reduced,which effectively promotes the rapid charge transfer between the grains,thus increasing the efficiency of CsPbIBr₂ perovskite battery devices from 8.9%to11.12%.In addition,the stability of the battery devices prepared by process optimization has also been significantly improved.