Organic–inorganic halide perovskites are emerging materials for photovoltaic applications with certified power conversion efficiencies(PCEs)over 25%.Generally,the microstructures of the perovskite materials are criti...Organic–inorganic halide perovskites are emerging materials for photovoltaic applications with certified power conversion efficiencies(PCEs)over 25%.Generally,the microstructures of the perovskite materials are critical to the performances of PCEs.However,the role of the nanometer-sized grain boundaries(GBs)that universally existing in polycrystalline perovskite films could be benign or detrimental to solar cell performance,still remains controversial.Thus,nanometer-resolved quantification of charge carrier distribution to elucidate the role of GBs is highly desirable.Here,we employ correlative infrared-spectroscopic nanoimaging by the scattering-type scanning near-field optical microscopy with 20 nm spatial resolution and Kelvin probe force microscopy to quantify the density of electrons accumulated at the GBs in perovskite polycrystalline thin films.It is found that the electron accumulations are enhanced at the GBs and the electron density is increased from 6×10^(19) cm^(−3 )in the dark to 8×10^(19) cm^(−3 ) under 10 min illumination with 532 nm light.Our results reveal that the electron accumulations are enhanced at the GBs especially under light illumination,featuring downward band bending toward the GBs,which would assist in electron-hole separation and thus be benign to the solar cell performance.展开更多
基金The authors sincerely thank professor Thomas Taubner and Dr.Martin Lewin for discussions on the calculation with the finite dipole model.This work was financially supported by NSFC(Grant 21727807,21872115,21902135)MOST(Grant 2016YFA0200703)and the Project funded by China Postdoctoral Science Foundation(Grant 2019M652251).
文摘Organic–inorganic halide perovskites are emerging materials for photovoltaic applications with certified power conversion efficiencies(PCEs)over 25%.Generally,the microstructures of the perovskite materials are critical to the performances of PCEs.However,the role of the nanometer-sized grain boundaries(GBs)that universally existing in polycrystalline perovskite films could be benign or detrimental to solar cell performance,still remains controversial.Thus,nanometer-resolved quantification of charge carrier distribution to elucidate the role of GBs is highly desirable.Here,we employ correlative infrared-spectroscopic nanoimaging by the scattering-type scanning near-field optical microscopy with 20 nm spatial resolution and Kelvin probe force microscopy to quantify the density of electrons accumulated at the GBs in perovskite polycrystalline thin films.It is found that the electron accumulations are enhanced at the GBs and the electron density is increased from 6×10^(19) cm^(−3 )in the dark to 8×10^(19) cm^(−3 ) under 10 min illumination with 532 nm light.Our results reveal that the electron accumulations are enhanced at the GBs especially under light illumination,featuring downward band bending toward the GBs,which would assist in electron-hole separation and thus be benign to the solar cell performance.
