Materials And Fabrication Technology Of Perovskite Solar Cell

Solar energy technology is a promising way to solve the energy problem of the world.High efficiency,low cost solar cells are the key of photovoltaic system.Currently,perovskite solar cells have attracted considerable interest due to rapidly increasing efficiency and low-cost solution-based fabrication method.The efficiency of perovskite solar cell in laboratory is comparable with efficiency of traditional silicon solar cell.However,perovskite solar cells do not meet industrial requirement at present and several issues must be dealt with.For example,although perovskite layer can be easily fabricated at low cost,other materials including Au counter electrode,hole transporting material and interface modification material in traditional perovskite solar cell are not cost-effective.In addition,fabrication process control needs to be improved.In this dissertation,we focused on the materials and fabrication process control of perovskite solar cell,the concrete results are as follows:(1)A new kind of low-cost small molecular hole transporting material,2TPA-n-DP(n=1,2,3,4),is synthesized.CH3NH3PbI3 perovskite solar cells with 2TPA-n-DP as hole-transporting materials are fabricated.Devices based on 2TPA-2-DP exhibits best performance.Up to 12.96% of power conversion efficiency of the device has been achieved,which is based on 2TPA-2-DP by optimization of mesoporous TiO2 film thickness,comparable to the device with Spiro-OMeTAD under similar conditions.Further,time-resolved photoluminescence measurement shows fast charge transfer process at perovskite/2TPA-2-DP interface.With the aid of electrochemical impedance spectra,study on electron blocking ability of 2TPA-2-DP in the device reveals that the existence of 2TPA-2-DP can greatly increase charge transfer resistance in the device,thus reducing the recombination.Besides,the perovskite solar cells based on these four hole-transporting materials exhibit good stability after one month test.(2)Reaction temperature as a key parameter has been introduced to manipulate the film deposition of the CH3NH3PbI3 absorber fabricated by the two-step solution deposition method.It is found that conversion time of CH3NH3 Pb I3 from dense Pb I2 layer can be significantly reduced by raising reaction temperature.CH3NH3PbI3 crystal grain sizes as well as surface roughness increase with reaction temperature.Influence of reaction temperature on perovskite film property has been investigated.Devices with CH3NH3PbI3 film deposited at higher temperatures exhibit better charge transport ability,larger built-in heterojunction field and weaker charge recombination,leading to enhanced solar cell performance.By optimizing reaction temperatures,as high as 17.40% and 14.02% of power conversion efficiencies of the mesoscopic and planar perovskite solar cells have been achieved,respectively.(3)Interfacial engineering toward the TiO2/perovskite interface has been demonstrated to be critical for achieving highly efficient perovskite solar cells.Perovskite solar cells with TiO2/perovskite interfacial modified by benzoic acid derivatives are fabricated.Influence of surface modification has been systematically investigated.No obvious influence of this interfacial modification on optical property,perovskite crystal structure and surface perovskite morphology are found according to XRD,absorption spectrum and SEM measurement.Enhancement of charge extracting ability of treated TiO2 and passivation toward traps of the TiO2 surface are confirmed by transient PL spectra and EIS measurement.Besides,effect of different groups on para-position is also investigated.Benzoic acid,para-Cl substituted benzoic acid,paraNH2 substituted benzoic acid and para-NO2 substituted benzoic acid have been studied in this work and para-Cl substituted benzoic treated device shows best performance.As high as 18.43% efficiency with maximal steady-state output efficiency of 17.19% has been achieved for the perovskite solar cell treated with para-Cl substituted benzoic acid,higher than efficiency of 17.19% and steady-state output efficiency of 16.17% obtained by untreated device.