Positive Effect Of Cathode Modifying Interlayers On The Performances Of Organic And Perovskite Based Solar Cells

Organic and perovskite solar cells are two groups of promising third generation solar cells.They exhibit very good power conversion efficiencies and in principle they can be fabricated with less expense and easy methods.To improve the efficiency and long-term stability of devices,“interlayers”show indispensable abilities in the interface engineering.This thesis mainly studied the positive effect of cathode modifying interlayers on the performances of organic and perovskite based solar cells.To be specific,we focused on the effects of a newly-designed zwitterion molecule,4-?2-hydroxyethyl amino?-6-?2-hydroxyethyl iminio?-3-oxocyclohexa-1,4-dien-1-olate?ZW-NH?,as cathode interlayer in the organic solar cells and a 2D Transition Metal Dichalcogenides?2D TiS₂?as cathode interlayer in the all-inorganic perovskite solar cells.The details are as follows:1.An alcohol-soluble zwitterion molecule,ZW-NH,was synthesized and used as cathode interlayer in the organic solar cells with inverted device structure.Compared with the control device using ZnO as the cathode interlayer,which exhibited PCE of 8.41%,the devices with ZW-NH as cathode interlayer showed PCE up to 8.98%,both in the PTB7-Th:PC₇₁BM organic system.Further,we modified the ZnO using ZW-NH.The solar cells with PTB7-Th:PC₇₁BM as active layer demonstrated the highest PCE of 9.22%while we added a layer of ZW-NH above the ZnO film.In addition,when we doped ZnO with ZW-NH,the devices incorporated ZW-NH doped ZnO as cathode interlayer showed increased fill factor?FF?.To analyze the reasons for the improved device performances while using ZW-NH as cathode interlayer alone,we looked into the light and dark properties of the solar cells.Furthermore,the devices with PTB7-Th:ITIC system also indicated higher PCE compared with control devices while using ZW-NH as cathode interlayer.2.We designed an ultrasound-assisted Li-ion intercalation reaction to prepare 2D TiS₂ water dispersion in the room temperature.The 2D TiS₂ water dispersion was spin-coated onto the ITO electrode to be utilized as cathode interlayer in the all-inorganic perovskite solar cells with n-i-p device structure.The all-inorganic perovskite was CsPbI₂Br,which was fabricated using the hot-plate spin-coating method.When the devices incorporated 2D TiS₂ as cathode interlayer alone,the highest PCE was 11.90%and the output at maximum power point can be stabilized at 11.41%for about 400 s.Furthermore,we modified the SnO₂ with 2D TiS₂.The devices with 2D TiS₂ modified SnO₂ illustrated a PCE up to 14.93%and the output at maximum power point can be stabilized at 14.42%for about 400 s.At the same time,the thermal stability and hysteresis phenomenon were better while the SnO₂/2D TiS₂ was incorporated.In addition,the trap-density in the devices was decreased dramatically.These results showed that the 2D TiS₂was a promising and potential cathode interlayer material which can improve the solar cells performances.