Research On The Application Of Low-temperature Prepared Mesoporous Tin Dioxide Films In Perovskite Batterie

The materials employed in the light absorption layers of high-efficiency perovskite solar cells(PSCs)is organic-inorganic hybrid lead metal halide perovskite materials,which have the advantages of high absorption coefficient and long carrier diffusion lengths.The power conversion efficiencies(PCEs)of PSCs have rapidly skyrocketed from 3.8%to 25.2%from 2009 to 2020,rivaling the performance of commercial silicon solar cells,which have been becoming the most promising candidate for commercialization in the near future.PSCs can be divided into mesoporous structure and planar structure according to the structures of the electron transport layers(ETLs).In terms of the development history of TiO2 as electron transport layers,we can see that photovoltaic devices fabricated based on mesoporous titanium oxide(m-TiO2)exhibit much better performance than planar titanium oxide(p-TiO2)as electron transport layers.Because the electronic extraction ability of mesoporous structure is more efficient than that of planar one.Furthermore,corresponding cells exhibit lower J-V hysteresis compared with planar structure.In recent years,PSCs with p-SnO2 electron transport layers have developed rapidly.By contrast,the preparation processes of m-SnO2 are relatively complex and a high-temperature sintering process is generally required.However,the hightemperature process is detrimental to the performance of SnO2.As such,p-SnO2 is rarely employed as the electronic transport layers at present.Thus,simplifying the fabrication process and avoiding high temperature sintering procedure to prepare m-SnO2 films is significant.In this context,we have successfully developed a simple low temperature process to prepare mSnO2 based electron transport layers.Compared with p-SnO2,it remarkably increases the electronic extraction ability,reduces J-V hysteresis effect,and improves the photovoltaic performance of devices.On this basis,m-SnO2 prepared through this method is applied to fabricate PSCs with TiO2/SnO2 double electron transport layers,which further improves the ability of electron extraction.The main research contents of this paper are as follows:1.The m-SnO2 was prepared as electron transport layers by using polyethylene glycol(PEG)as pore forming agent with a low temperature process.A two-step spin coating method was used to deposited perovskite films.The efficiency of electron transport from the perovskite films to ETLs were increased.The mesoporous ETLs were prepared by spin-coating the mSnO2 precursor solution with the addition of PEG through a low temperature process.The formation of mesoporous structure increases the contact area between the perovskite films and the ETLs.The increase of the contact area permits more electrons pass through the interface to the ETLs,thus the ability of the electron transport layer to extract electrons is improved.The structure of the photovoltaic devices is ITO/p-SnO2/m-SnO2/perovskite/Spiro-OMeTAD/Ag.When the PEG concentration in precursor solution was 6%(volume ratio),corresponding devices exhibited the best photovoltaic performance and a maximum PCE of 20.82%was achieved.Besides,the filling factor(FF)and short-circuit current density(Jsc),which can reflect the electronic extraction ability,were significantly improved.2.The m-SnO2 films were applied to the TiO2/SnO2 double-layer electron transport layers to form the TiO2/SnO2/m-SnO2 three-layer electron transport layers.It has been reported that the TiO2/SnO2 double electron transport layer shows better electronic extraction capacity than the TiO2 or SnO2 single ETL.In this regard,the mesoporous structure is applied to the double electron transport layers to further improve the electronic extraction capacity of the ETLs.The configuration of the device is FTO/p-TiO2/p-SnO2/m-SnO2/perovskite/Spiro-OMeTAD/Ag.Benefited from the novel structure of the ETLs,FF as high as 78.7%of the devices were obtained,which indicated that the electronic extraction capacity is better than the single ETLs and the TiO2/SnO2 double ETLs.For simplicity,in my research works,PEG was introduced as a pore-forming agent,and m-SnO2 films were prepared as ETLs through a low temperature process,which improved the electronic extraction ability of the ETLs.The application of mSnO2 film to the TiO2/SnO2 double electron transport layers further improved the electronic extraction capacity.