Effect Of Interface Modification On The Photovoltaic Performance Of Inverted Perovskite Solar Cells

In recent years,organic-inorganic hybrid perovskite solar cells have been a hot-spot in the field of photovoltaic research due to their excellent performance,such as simple preparation process,low cost and high power conversion efficiency.In last decades,the photovoltaic performance of perovskite solar cells had made great progress.At present,the poor stability and hysteresis of perovskite solar cells impeded its commercial application.One reason is that the perovskite thin film solar cell as a solar cell,there is a contact interface between the various functional thin film.Studies have shown that photogenerated carriers in the device at each interface recombination velocity is much larger than the body of material complex perovskite phase.Thus,the interface modification and control can be an effective means of suppressing the recombination rate of carriers for the perovskite solar cells to enhance the photoelectric conversion efficiency.The interface modification can enhance the carrier mobility,the conversion efficiency and the stability of the device.In this thesis,the effect of small molecule copper bath on perovskite solar cell performance and NH₄X?X=F^-,Cl^-,I^-?materials as interface modification layer on the performance of NiO_x based perovskite solar cells were studied by means of interface modification,respectively.1.The inverted perovskite solar cell ITO/PEDOT:PSS/CH₃NH₃PbI₃/PCBM/BCP/Ag was prepared,in this structure small molecular bathocuproine?BCP?was introduced between the electron transport layer and cathode as a buffer layer.The power conversion efficiency?PCE?of perovskite solar cells and the impact of transmission characteristics of the carrier were studied.Compared with perovskite solar cells without BCP buffer layer?power conversion efficiency is 9.67%?,the maximum power conversion efficiency?PCE?of the devices with the BCP buffer layer could be increased to 13.06%when the spinning speed of BCP layer is 5000 rpm.The BCP buffer layer reduced the charge transfer resistance,improved the cathode's electron collection capacity,and enhances the photovoltaic performance of perovskite solar cells.2.In order to optimize the photovoltaic performance of ITO/NiO_x/MAPbI₃/PCBM/BCP/Ag devices,the influence of fabrication processes for NiO_x hole transport layer,MAPbI₃ perovskite active layer,and PCBM electron transport layer on the device performance were systematically studied.Under the fabrication process which NiO_x hole transport layer two times spin coated and the heated at 320?,the anti-solvent dropped at 40 s during the spinning process of active layer,the spin coated PCBM film was placed in the glove box nitrogen environment for 10 min,and then annealed at 95?,possibly enhanced the device performance.After the optimization of the preparation process,the maximum power conversion efficiency?PCE?of the device was 13.75%,the open circuit voltage(V_oc)was 1.05 V,the short-circuit current(J_sc)was 19.39 mA/cm²,and the filling factor?FF?was 67.53%.3.NH₄X?X=F^-,Cl^-,I^-?as the interface modification layer was utilized in the perovskite solar cell with the structure of NiO_x/NH₄X?X=F^-,Cl^-,I^-?/CH₃NH₃PbI₃/PCBM/BCP/Ag.The influence of interface modification by using NH₄X?X=F^-,Cl^-,I^-?on the performance of perovskite solar cell was investigated.The results show that the photovoltaic parameters,such as V_oc,J_sc,FF and PCE are significantly improved and the devices have no hysteresis after the NH₄X?X=F^-,Cl^-,I^-?modification.Among them,the device with NH₄I modification has the best performance,and the photovoltaic performance parameters are V_oc=1.07 V,J_sc=20.80 mA/cm²,FF=69.18%,and PCE=15.33%.The external quantum efficiency spectrums of the devices showed that the interface modification employing NH₄X?X=F^-,Cl^-,I^-?significantly improved the charge collection,and enhanced the photovoltaic performance of the device.Impedance analysis shows that the introduction of NH₄X?X=F^-,Cl^-,I^-?layer reduced the charge transfer resistance of the device,increased the composite resistance of the electron and hole,which facilitates the transmission of the hole and electron from the perovskite layer to the corresponding electrode after the separation,and reduced the recombination rate of the electron and hole.Compared with the reference device,charge transfer resistance of the device with NH₄I layer is the minimum?R_h=1.35??,and the charge composite resistance was the maximum(R_rec=119?).The defect density analysis of the devices showed that the introduction of NH₄X?X=F^-,Cl^-,I^-?layer reduced the interface defects of NiO_x/MAPbI₃,decreased the non-radiative recombination,and thus increased the current density of devices.Under N₂ protection,the efficiency of device with NH₄I layer remained above 90% of the initial efficiency after a week.However,the PCE of the reference devices seriously decreased 30%of the initial efficiency.The interface modification based on NH₄X?X=F^-,Cl^-,I^-?improved the stability of devices.