The Study On The Carrier Recombination Process Of CsFAMA Triple-cation Perovskite Film

In the continuous research on solar cells,it has been found that perovskite solar cells have obvious advantages in conversion efficiency compared with other solar cells.At the same time,perovskite solar cells have a relatively simple manufacturing process and excellent characteristics,so they are becoming more and more popular in the photovoltaic field.In this context,further understanding of the optoelectronic properties of perovskite materials is of great value for continuing to improve the conversion efficiency and the application of perovskite materials.This thesis studied the photoluminescence process and microwave photoconductivity response of the CsFAMA triple-cation perovskite.Obtained the information of the carrier recombination process.The mainly conclusion of the study is divided into two parts:First,the thesis has studied the photoluminescence process of CsFAMA triple-cation perovskite film at different thermodynamic temperatures and different excitation light intensities by the steady-state fluorescence(PL)and time-resolved photoluminescence(TRPL)spectrum measurement techniques.The experimental results shown that the luminous peak position of CsFAMA perovskite film at room temperature was about 1.6 eV,and the band gap obtained by transmission spectrum was 1.61 eV.The luminous peak position was slightly smaller than the band gap,which confirmed the existence of a tail-state luminescence process.Changing the thermodynamic temperature from 15 K to 295 K.The results confirmed that the center wavelength of the PL spectrum showed a blue shift trend,but after 245 K,it showed a red shift trend.And the full width at half maximum of the PL spectrum is more obvious after 245 K towards the lower energy side.Compared the PL spectra of CsFAMA perovskite films at three typical thermodynamic temperatures of 15 K,175 K,and 285 K.The results found that a "shoulder" appeared at 1.55 eV at a thermodynamic temperature of 285 K.Further using the TRPL measurement technology to measure the fluorescence lifetime.The results found that the fluorescence lifetime increased in the range of 15 K-150 K,and basically unchanged in the range of 150 K-245 K.But above 245 K,the fluorescence lifetime decreased rapidly.The thesis proposed that there was a phenomenon of energy transfer from triple-cation perovskite to single-component perovskite after the thermodynamic temperature was greater than 245 K.Second,the thesis has studied photogenerated carrier concentration and composited kinetic information of CsFAMA perovskite film at different excitation light energy and different thermodynamic temperatures by the microwave photoconductive technology.The carrier recombination lifetime was obtained by double exponential fitting.For the triple-cation perovskite,the carrier recombination lifetime decreased with the increase of the excitation light energy.This is because as the excitation light energy increases,the second-order electron-hole recombination and the third-order Auger recombination lead to an increased rate of carrier decay.Changing the thermodynamic temperature from 74 K to 304 K.The results found that the carrier lifetime increased when the thermodynamic temperature rose to around 104 K.When the temperature continues to rise,the lifetime decreased.This thesis attributed this phenomenon to the intensification of non-radiative recombination.Based on the signal amplitudes at different thermodynamic temperatures,the changes in the relative yield of photogenerated carriers was also discussed.Compared with the condition of 74 K,the relative carrier yield at 304 K increased by about 13.5 times.This thesis temporarily attributed the increase of carrier concentration with temperature to thermal energy that accelerates exciton separation and generates more free carriers.