Research On The Interface Modification Of TiO₂ Electron Transport Layer In Perovskite Solar Cells

With the sustainable development and progress of society,there are problems of energy scarcity and environmental pollution.Facing with these problems,a large number of scientific researchers are working hard to explore and develop new,clean energy for replacing non-renewable and traditional fossil energy.Solar energy is a new energy source with abundant reserves and environmental impact.At present,silicon-based solar cells are the most effective way to utilize solar energy.However,silicon-based solar cells have complex preparation process,expensive production costs and accompanying environmental pollution.To solve these problems,scientific researchers with great interest explore low-cost,environmentally friendly thin film solar cells.Since 2009,perovskite solar cells(PSCs)have been favored by a large number of researchers due to their high conversion efficiency,simple preparation process,low cost and large area preparation.Ti02 has become the most commonly used electronic transporting material because of its suitable conduction band position,wide band gap,strong electronic transmission ability,excellent light transmittance and low production cost.However,some problems still exist in the TiO2 as electronic transporting layer,which affect the conversion efficiency of perovskite solar cells:(1)low conductivity;(2)high defect density of thin films,which is prone to carrier recombination;(3)mismatch for energy levels between TiO2 and perovskite layer will affect electron injection efficiency and open circuit voltage of cells.Aiming these problems,the interface modification method is used to improve the power conversion efficiency of the perovskite solar cells.The research conclusions are as follows:1.Silane(?-MPTS)modified mesoporous TiO2 electron transport layer.y-MPTS is chemically adsorbed on the electron transport layer of mesoporous TiO2 through dehydration condensation.Because y-MPTS has a certain length of alkyl chain,it is equivalent to form a thin insulating layer between MAPbl3 and mesoporous TiO2,which causes to tunnel effect and reduces the recombination of interface electrons and holes.The formation of hydrogen bond between-SH of the y-MPTS terminal and I-of the perovskite layer is beneficial for reducing the density of defect states on the surface of perovskite layer and improving the quality of perovskite layer film.When the lOmM concentration of the y-MPTS solution modified the mesoporous TiO2 film,the PCE increased from 14.36%to 16.50%.2.Rare earth element Ce doped mesoporous TiO2 electron transport layer.On the one hand,the bottom of conduction band is moved up by doping with cerium into mesoporous TiO2 that has better energy level matching between the perovskite layer(MAPbI3)and titanium dioxide(TiO2),which improves the injection efficiency of electrons,reduces the recombination of electrons and holes,and improves the open-circuit voltage of the battery.On the other hand,the doping of Ce into mesoporous TiO2 results in lattice distortion of TiO2,changes its crystallization process,and further improves the morphology of titanium dioxide.When the concentration of Ce3+ions is 2%,the energy conversion efficiency of the cell is 17.75%.3.DNA-modified mesoporous TiO2 electron transport layer.On the one hand,DNA-modified mesoporous TiO2 can reduce the defect density of mesoporous TiO2,and improve the effective electron injection;on the other hand,DNA-modified mesoporous TiO2 can change the crystallization process of mesoporous TiO2,optimize the morphology of titanium dioxide and facilitate charge transfer.Moreover,mesoporous TiO2 has not been annealed,which reduces the cell preparation process.When DNA concentration is 0.2 mg/mL,the cell achieves 17.59%efficiency.