Study On Fabrication And Stability Of High Performance Perovskite Solar Cells

Perovskite solar cells?PSCs?have been established as the most important new candidate for next generation photovoltaics,due to the excellent photoelectric property,facile fabrication process and high power conversion efficiency?PCE?.PSCs are mainly composed of transparent conductive substrate,electron transporting layer?ETL?,perovskite absorber,hole transporting layer?HTL?and counter electrode.Especially,film quality of perovskite absorber and conductivity of ETL directly affect the device performance of PSCs.With the improvepment of PCE,long-term device stability is another grand challenge to be offset before the further development and commercialization of PSCs.Therefore,our works focus on the improvement of PCE and device stability of PSCs,mainly involving fabrication of high-quality perovskite film,improving the conductivity of ETL,surface-interface engineering of perovskite film,constructing high-efficiency and stable carbon-based PSCs,and so on.Our typical achievements are summarized as following:Firstly,a repeated interdiffusion method is described for phase-stable and high-quality perovskite film.The crystallization and growth of perovskite film can be well controlled by adjusting the reactant concentrations.With this method,smooth perovskite film with large crystals has been obtained.Finally,a PCE of 16.5%as well as a steady-state efficiency of 16.3%are achieved in planar PSCs.Secondly,Mg as an effective ion dopant has been introduced into compact TiO₂ETL for planar PSCs.It is found that Mg doping can shift the Fermi energy level of TiO₂ upward and decrease the resistivity of TiO₂ film.Carrier transport velocity is thus enhanced and high charge collection efficiency has been achieved at high voltages,leading to a higher fill factor and better cell efficiency.A PCE of more than19%has been obtained,which is one of the best achieved efficiencies for planar PSCs.Thirdly,we directly employ polystyrene?PS?to assist the deposition of perovskite film in one-step anti-solvent method.The PS could cover on the film surface and be pushed to the grain boundaries during the perovskite crystallization process,forming PS-capped perovskite grains.This PS coverage could block the mass exchange between perovskite grains and external environment,thus suppressing the organic component evaporation and water corrosion.Finally,the perovskite film shows better stability in chemical phase,morphology,and microstructure under extreme conditions and can fast heal itself after water degradation.Moreover,it is found that this PS assisted film deposition could help to reduce the charge traps and nonradiative recombination of the perovskite semiconductor.The PCE of PS-based planar PSCs is thus promoted to 20.2%with a steady-state efficiency of 19.3%,and could retain its 90%after 30 days kept in the ambient conditions.Finally,we prepare a kind of macroporous carbon film by room-temperature solvent-exchange method.The prepared carbon film possesses good flexibility,compressibility and adhesivity owing to the macroporous structure.It exhibits tremendous advantage as counter electrode for HTM-based PSCs.When being transferred onto underlying hole transporting layer by press method,the macroporous carbon electrodes can closely adhere to HTL due to its compressibility and adhesivity.The transient photocurrent measurement indicates fast interface charge transfer between macroporous carbon film and HTL,suggesting excellent interface property.Finally,we obtain a high PCE of 19.2%for mesoporous-structure PSCs,which is the best achieved for carbon-based PSCs.Besides,the flexible carbon film can be rolled up without performance loss,showing great potential for the flexible devices and roll-to-roll manufacturing.Further stability test reveals that under the ambient condition,over 95%of the initial efficiency has been retained after more than 1000hours storage,suggesting that corrosion and water resistance of the macroporous carbon electrodes can effectively help to improve the device stability.