| In recent years,perovskite solar cells have been considered as promising photovoltaic devices due to their simple preparation process,adjustable band gap,high carrier mobility,high absorption coefficient and low defect density.In about ten years,its photoelectric conversion efficiency has rapidly increased from 4% in 2009 to 25.5%,but it still faces great challenges in manufacturing market-oriented high-performance perovskite solar cells.At present,the power conversion efficiency of commercially available large-area perovskite solar cells is not high.Among them,the functional layer is one of the main factors that determine the performance of the device.First,the light absorption layer prepared from the perovskite itself,on the one hand,due to the different properties of the perovskite of different components,the best component of the perovskite is selected.Ore is very necessary;on the other hand,the shallow-level defects or deep-level defects that cannot be avoided in the crystallization process of perovskite,the passivation of these defects is also the key to improving the performance of the device.Secondly,since the electron transport layer and hole transport layer are responsible for the conduction of electrons and holes,the optimization of them is also extremely important.This article mainly explores the optimization of the light absorbing layer,the hole transport layer and the interface layer between the two.First,the efficiency and stability of the devices prepared by two perovskite materials with different band gaps,Cs0.05(FAPb I3)0.85(MAPb Br3)0.15 and(FAPb I3)0.92(MAPb Br3)0.08 were studied.(FAPb I3)0.92(MAPb Br3)0.08 has a lower band gap(about 1.56 e V),which can bring more photocurrent to the device to improve efficiency,and has better film quality,so it also has excellent air stability.It laid the foundation for the next preparation of devices with high efficiency and excellent stability.Then,the gold nanorod aqueous solution was added to the perovskite precursor solution,hoping to optimize the(FAPb I3)0.92(MAPb Br3)0.08 type perovskite through the asynchronous synergistic effect of the gold nanorod aqueous solution.Studies have shown that the LSPR effect of Au NR increases the light absorption and exciton separation inside the perovskite,which greatly increases the current of the device while keeping the voltage basically unchanged.The addition of a small amount of water promotes the recrystallization process of the perovskite,improves the quality of the perovskite film and the size of the crystal clusters,reduces its internal defects,and increases the stability of the device.The power conversion efficiency of the final device reached 21.73%,and the unpackaged device remained 95% of its initial efficiency after being stored in air for 90 days.Finally,two donor-acceptor graphene derivatives DA NG-t Bu and DA NG-OMe are used to passivate the upper surface of(FAPb I3)0.92(MAPb Br3)0.08 type perovskite while also optimizing the hole transport layer.Studies have shown that these two molecules are rich in electron donors,which can effectively passivate perovskite surface defects and carry out P-type doping,which can bend the energy band of perovskite and better match the hole transport layer,thereby increasing the device voltage.In addition,the molecules partially dissolved in the hole layer can also increase the hole mobility and increase the current of the device.Finally,by introducing these two molecules,the power conversion efficiency of the best device can be increased to23.5% and 23.2%.And the unpackaged device can still maintain 95% and 93% of its initial efficiency after being stored in the air for 3000 hours. |
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