Enhancing The Photovoltaic Performance Of Perovskite Solar Cells With MXene Doped Electron Transport Layer

Perovskite solar cells(PSCs)have received widespread attention and developed rapidly due to their low cost,easy-manufacturing and flexible characterisitics.The efficiency of PSCs has increased rapidly from 3.8%to 25.5%,which is comparable to the monocrystalline silicon solarcells.The interface between the electron transport layer and the perovskite layer plays a vital role in the interfacial elelctron injection and electron-hole recombination dynamics,which is closely related to the overall photovoltaic performance of PSCs.As the most commonly used and ideal electron collection and transport material in PSCs,TiO2 is always riddled with defects both inside and on the surface,which usually act as recombination centers,accelerating the non-radiative recombination,thus affecting the photoelectric conversion efficiency of PSCs.Meanwhile,the directional movement of the defects in TiO2 under different photovoltage scanning results in different interfacial electronic dynamics and severe photocvurrent-photvoltage hysteresis.In addition,the defects of TiO2 can accelerate the degradation of perovskite layer,affecting the stability of the device.Ti3C2Tx MXene has advantages of high conductivity,high light transmittance,matched work function with the energy levels of perovskite and TiO2.In this paper,Ti3C2Tx MXene is used to dope the TiO2 electron transport layer(ETL)to optimize the photovoltaic performance of PSCs.Compared with the control device,the efficiency of the device doped with mxene has been increased by 8%(from 19.27%to 20.80%),and the stability has also been significantly enahanced.Through scanning electron microscopy(SEM),electrochemical impedance spectroscopy(EIS),photoluminescence(PL),time resolved photoluminescence(TRPL)and ultraviolet photoelectron spectroscopy(UPS)and other methods,we have found that:1.Compared with the control device,the perovskite films deposited on the Ti3C2Tx-MXene doped ETL film is more uniform and smoother with larger grain size,which is due to the more hydrophilic property of MXene-doped ETL with smaller wetting angle,promoting the crystallization of perovskite and improving the film quality.In addition,the terminal group-F of Ti3C2Tx-MXene can fill the halogen defects of perovskite materials,thus reducing the electron-hole recombination and perovskite degradation caused by defects,resulting in significantly improved efficiency and stability of the device.2.Benefitting from the high conductivity of MXene,the electron transport impedance of ETL has been significantly reduced,accelerating the electron transport to the ITO conductive substrate,leading to decreased interfacial charge recombination,thus improving the electron collection efficiency of the device.3.Doping with MXene can adjust the work function of TiO2 ETL from 3.83 eV to 3.98 eV,giving rise to larger driving force for electron injection and smaller driving force for electron-hole recombination,speeding up the interface electron injection and slowing down the interface electron-hole recombination,consequently improving the efficiency of PSCs.