| Organic-inorganic hybrid perovskite solar cells(PSCs)have developed at an alarming rate,and have attracted widespread attention in the scientific community since 2009.The organic-inorganic perovskite materials have many excellent characteristics,including low exciton energy,high carrier diffusion length,high carrier mobility,low carrier recombination rate,suitable band gap,and without rare elements,etc.Benefiting from these merits,the power conversion efficiency(PCE)of PSCs has increased from 3.8%to 22.7%in a few years,exceeding that of the amorphous silicon solar cells and thin film solar cells.In addition,the stability of PSCs has also improved.Although the PCE of PSC has exceeded 20%,there is still a long way to go before their real commercialization,because PSCs still face many challenges that are not well resolved such as irreproducible fabrication process,inferior device stability,and anomalous effect.Currently,high-performance PSCs are usually fabricated by one-step methods using toxic anti-solvents such as chlorobenzene,toluene,etc.The fabrication of PSCs using these toxic anti-solvents has many disadvantages,including high toxicity,high cost,poor reproducibility,and high requirements for preparation process.The lack of anti-solvents that have good reproducibility for device fabrication and less dependence on ambient condition,severely restricts the application of PSCs.Moreover,most of the high performanced PSCs have conventional device structures,which use TiO2 as the electron transport layer(ETL).However,the low electron mobility of TiO2 leads to the accumulation of electrons at the interface and contributes to the hysteresis effect,which greatly affects the accurate evaluation of the device performance of PSCs.Besides,due to the photocatalytic properties of TiO2,it will generate oxygen vacancies under the irradiation of ultraviolet light,accelerating the decomposition of perovskites and causing deep defects,which finally becomes a center of recombination to reduce the efficiency and stability of PSCs.In view of the use of toxic anti-solvents,poor reproducibility for device fabrication and the drawbacks of TiO2 ETL,we developed a novel green anti-solvent to prepare high-performing,high reproducible perovskite solar cells,and synthesized a novel fulleropyrrolidine derivative to modify the surface of TiO2,and the main results and conclusions were carried out as follows:(1)For the first time,we used di-isopropyl ether as a green anti-solvent to fabricate highly efficient and reproducible PSCs.Compared with the conventional anti-solvents(toluene,chlorobenzene,chloroform,etc)treatment,perovskite thin films fabricated by di-isopropyl ether have larger crystal grains,better crystallinity,and fewer defects,which makes the maximum efficiency of the device reaches 19.07%.To verify the high reproducibility of the devices fabricated by di-isopropyl ether,60 devices were fabrication with average PCE of 17.67%± 0.54.Moreover,compared with diethyl ether,the higher boiling point of di-isopropyl ether(68.3 ?)makes it an excellent anti-solvent,which greatly enhances the tolerance to elevated ambient temperature.The efficiency of PSCs is still as high as 16.75%even though the process was conducted at temperatures up to 40?,which makes di-isopropyl ether a suitable anti-solvent for mass production of PSCs.(2)A novel fulleropyrrolidine derivative(FPTPA)was synthesized and used as an interfacial modifier for the TiO2 ETL in PSCs.The crystallinity and film quality of perovskite film fabricated on FPTPA modified TiO2 substrates were greatly improved with fewer defects.The FPTPA modification layer can effectively improve electron extraction,passivate trap states on the TiO2 surface,and suppress charge recombination.As a result,a PCE as high as 19.10%with a maximal steady-state output PCE of 17.65%was achieved for the TiO2/FPTPA devices with alleviated hysteresis and enhanced light soaking stability. |
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