Performance Improvement Of Organic And Perovskite Solar Cells By Interfacial Modification And Acitve Layer Modification

Solar energy is the most ideal and safe energy for human being.It is inexhaustible,and its utilization can effectively solve the problem of global energy shortage.As the new generation of solar cells,polymer solar cell and perovskite solar cell have been widely studied by the researchers all over the world because of their many excellent properties.Interfacial modification and active layer modification are two common ways to improve the performance of polymer or perovskite solar cells.In this paper,the ZnO electron transport layer has been modified by O doped ZnS nanocrystals（NCs）in polymer solar cell based on PTB7-Th:PC71BM active layer.The PC₆₁BM electron transport layer has been modified by SnO2 NCs in inverted perovskite solar cell based on CH3NH3PbI3 active layer.The performance of both the solar cells is improved by the interfacial modification as mentioned above.Moreover,NaIO4 has been chosen to modify the CH3NH3PbI3 perovskite active layer,successfully improving the device performance to some extent.The main results are as follows:A solution method was adopted to prepared O doped ZnS（ZnS（O））colloidal NCs.The as-prepared NCs have been proved to be consistent with the crystal structure of ZnS and Zn3d-O 2p hydrization existed in the as-prepared NCs as certified by O k-edge X-ray absorption spectra（XAS）.The average size was measured to be about 8.5 nm by Transmission Electron Microscope（TEM）.The role of pyridines was to control the size and tune the surface property.By doping oxygen into ZnS lattice,the energy levels of as-prepared NCs were moved down,giving a better band alignment for photovoltaic application.When it was applied to modify ZnO interlayer and form ZnO/ZnS（O）bilayer in the polymer solar cells（PSCs）,the optimal power conversion efficiency（PCE）of the device based on ZnO/ZnS（O）reached 8.85%,which increased by 10%compared to ZnO-only control device with the optimal PCE of 8.00%.PC₆₁BM:SnO2 electron transport layers（ETLs）were applied in inverted CH3NH3PbI3perovskite solar cells and a high power conversion efficiency of 19.7%could be obtained.It increased by 49%in comparison with the device based on PC₆₁BM-only ETL（13.2%）.SnO₂ nanocrystals with excellent dispersibility were employed here to fill the pin-holes and cover the valleys of PC₆₁BM layer,forming smooth and compact PC₆₁BM:SnO₂ layers.Simultaneously,the electron traps caused by deep-level native defects of SnO2 were reduced by PC₆₁BM proved by the space charge limited current analysis.Thus,PC₆₁BM:SnO₂ ETLs can inhibit both of the defects in PC₆₁BM and SnO₂ layers which contribute to the electron transport improvement and reduce the recombination loss.Moreover,the device stability based on the bilayer was significantly improved in comparison with the PC₆₁BM-only device and the performance of 85%could be maintained after one month.NaIO₄ was adopted to modify CH₃NH₃PbI₃ perovskite precursor solution and larger crystal size could be achieved in the film prepared by the precursor solution.The energy band gap of the MAPbI₃ was narrowed by means of the modified method,which could make it absorb more light and produce more photogenerated carriers.In addition,the modified method reduced the density of deep level electron defects in perovskite film and suppressed the non-radiation recombination.Finally,the modified perovskite film was applied in inverted perovskite solar cell which obtained a PCE of 15.53%.Compared with the PCE（13.14%）of unmodified device,it increased by 18%.