| Perovskite solar cells(PSCs)have received widespread attention from researchers around the world,owing to its ease of preparation,low cost and high efficiency.Among the various components of PSCs,the electron transport layer,which acts for transporting electrons and blocking holes,is critical.And it plays a vital role in improving cell efficiency and relieving hysteresis.The most widely used electron transport layer material is TiO2.Anatase TiO2(A-TiO2)is a commonly used material for high-efficiency batteries,its application still has some problems.For example,lower electron mobility results in electron accumulation at the interface between the electron transport layer and the perovskite,thereby reducing efficiency and causing large hysteresis effect.Therefore,various means have been tried to further improve the performance of the electron transport layer.The rutile phase TiO2(R-TiO2)has a higher electron mobility and better lattice matching with the perovskite.However,the rutile phase TiO2 is rarely used in the electron transport layer of perovskite solar cells.In addition,for the mesoporous layer,very little research has been conducted on hollow sphere materials,which have light scattering effects.Therefore,in order to solve these problems,the rutile phase TiO2 compact layer was prepared,and the influence of preparation conditions on the compact layer and the battery was studied systematically.The difference of anatase(A-TiO2)and rutile phase structure was studied in detail,and their impact on the performance of the battery.Additionally,the TiO2 hollow spheres were prepared for mesoporous layers,and the influence of hollow spheres on the photoelectric properties of PSCs was studied in detail.The main findings are as follows:1.A rutile phase TiO2 compact layer was successfully prepared by a new TiO2 preparation method.The system regulates deposition time and sintering temperature.As the sintering temperature increases,the crystallinity of TiO2 becomes better,the oxygen vacancies decrease,and the roughness first decreases and then increases.The R-TiO2 compact layer sintered at 500 ℃ has the strongest electron separation ability,and can transmit the photogenerated electrons in the perovskite to the FTO as soon as possible.Thus,it obtains higher VOC and FF,thereby achieving an efficiency of up to 20.8%.In addition,the method is simple in preparation and low in cost.2.When R-TiO2 is compared with A-TiO2,R-TiO2 has a higher lattice matching degree with MAPbl3,and better wettability with the perovskite precursor solution.The electron mobility of R-TiO2 is also higher,and the density of trapped states is lower.In the IMPS and IMVS tests,the results show that the battery prepared by the R-TiO2 compact layer has a longer electron lifetime and a faster diffusion rate.Therefore,the R-TiO2 assembled battery achieves superior photoelectric conversion performance while greatly alleviating the hysteresis effect.3.Using carbon hydrothermal condensation reaction of glucose,carbon spheres of 300 nm,400 nm and 800 nm were synthesized.Using these carbon spheres as templates,50 nm,100 nm,and 200 nm TiO2 hollow spheres(TiO2 HS)were synthesized.These hollow spheres have only a thin outer shell layer with uniform micropores on the shell.XRD patterns show that the TiO2 hollow spheres are pure anatase phase.As the size of TiO2 hollow spheres decreases,its photoelectric properties gradually increase.50 nm TiO2 HS achieved optimal performance and eliminated hysteresis.The performance of the battery prepared by P25 as a control group was between 100 nm TiO2 HS and 200 nm TiO2 HS.The battery prepared by 50 nm TiO2 HS has a longer electron lifetime and a faster transfer rate.Its electron extraction capability is also the strongest.In addition,50 nm TiO2 HS effectively reduces the density of defect states,which may be attributed to its cavity fraction,reduced defects,and the ability to adsorb more perovskites.Therefore,it is possible to improve the efficiency while eliminating hysteresis. |
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