Highly Efficient And Low-Cost Planar Perovskite Solar Cells With Low Synthesis Temperature

Since it came out in 2009,perovskite solar cell technology has made a great breakthrough in the last 10 years.According to the latest report,the power conversion efficiency of perovskite solar cells has exceeded 25%,making the commercialization of this burgeoning photovoltaic technology very promising.The commercialization of an emerging solar cell technology depends on whether a balance among efficiency,stability and cost can be achieved.At present,the efficiency of perovskite solar cells has reached 25.2%,which is higher than that of polycrystalline silicon based solar cells and CIGS solar cells that have been widely commercialized.Compared with the beginning of the development of this photovoltaic technology,the stability of perovskite solar cells has been greatly improved.Perovskite solar cell that was able to work stably for one year have been reported in 2015.The cost of perovskite solar cells mainly comes from two aspects:The use of expensive raw materials such as Spiro-OMeTAD,Au,PCBM,and the high-temperature annealing process for the preparation of electron transport layer and perovskite absorption layer during the fabrication of perovskite solar cells.In this thesis,low-temperature fabricating technique is developed to prepare electronic transport layer and perovskite light absorbing layer,and low-cost hole transport material and high stability hybrid perovskite material are synthesized to reduce the manufacturing cost of perovskite solar cells and prepare high-efficiency and stable perovskite solar cells,contributing to the commercialization of this emerging solar cell technology.High-quality tin oxide films were prepared at room temperature applying pulse laser deposition technique,replacing TiO₂ as electron transport layer in perovskite solar cells.Compared to that of the traditional TiO₂ fabricating process,which requires high temperature(500?)annealing to get better performance,the energy consumption during the preparation of perovskite solar cells can be effectively reduced by using pulse laser deposition technology to prepare SnO₂ electron transport layer at room temperature.At the same time,a simple two-step spin-coating method was used to prepare perovskite-PCBM bulk heterojunction light-absorbing layer,greatly suppressing the current density-voltage(J-V)hysteresis effect of the perovskite solar cell.A novel transport material Cz-OMeTAD has been designed and synthesized using low-cost raw material carbazole through a facile three-step synthesis method.Compared to the conventional hole transporting material Spiro-OMeTAD,the synthesis cost of Cz-OMeTAD is only 1/20 of that of Spiro-OMeTAD.However,the conductivity,hole mobility and alignment with perovskite layer of Cz-OMeTAD are at the same level as Spiro-OMeTAD.Perovskite solar cells based on Cz-OMeTAD hole transport layer achieved comparable efficiency to that of Spiro-OMeTAD hole transport layer based devices.Triple cation perovskite(MA_0.7FA_0.3)_1-2xEDA_xPbI₃ has been developed by incorporating ethylenediamine(EDA²⁺)in the double cation perovskite system.Compared to conventional monovalent ammonium ions,the two NH₃⁺on the ends of EDA²⁺could be connected to surrounding PbI₆^4-units by van der Waals forces,which can stabilize the perovskite lattice structure,significantly improving the stability and efficiency of the prepared perovskite solar cells.?-FAPbI₃ black phase perovskite films were prepared at room temperature without any thermal annealing or vacuum process through a facile spin-coating method by incorporating a mixture of formamidine thiocyanate and methylamine thiocyanate in the perovskite precursor solution,which can reduce the fabricating cost and the energy payback time of photovoltaic devices,in favor of developing flexible perovskite solar cells.