Optimization Design And Theoretical Research Of Perovskite Solar Cells

Recent years,organic-inorganic halide perovskite have attracted tremendous research attention due to high absorption coefficient,high carrier mobility,long carrier lifetime,and tunable band gap.Benefiting from these excellent optoelectronic properties,halide perovskites could be widely used in solar cells,light emitting diodes,field effect transistors,photodetectors,etc.In perovskite solar cell,both spin coating and printing process are suitable to prepare the device,which makes it possible to commercialize perovskite solar cell.In addition,perovskite materials can also be deposited on flexible substrates and applied to flexible devices.The power conversion efficiency（PCE）of perovskite solar cell has reached 25.5%,however,it is still lower than Shockley–Queisser limit.Therefore,single-junction perovskite solar cells is investigated in this work firstly.Then,in order to improve the photon absorption,perovskite/GIGS tandem solar cell is explored as well.After that,anisotropy effect of single crystal perovskite is investigated owing to the lower defect density,longer carrier diffusion length and the absence of grain boundary,etc.Finally,the potential nontoxic and stable perovskite material for high-performance solar cell is investigated.The related research results are as follows:1.Single-junction perovskite solar cellDrift-diffusion model is employed to explore normal perovskite solar cell（FTO/SnO₂/CH₃NH₃PbI₃/spiro-OMe TAD/Ag）.In detail,electrode workfunction,thickness of each layer,and energy band offset are investigated.According to the results,the optimal thickness of perovskite layer,SnO₂ electron transport layer,and spiro-OMe TAD hole transport layer are 500 nm,40 nm,and 70 nm respectively.The optimal conduction band offset is-0.1～0.4 eV,optimal valence band offset is-0.1～0.1 eV.In addition,the optimal PCE is achieved when cathode electrode work function is larger than-4.8 eV,and anode electrode work function is smaller than-5.2 eV due to increased built-in voltage.2.Double-junction perovskite solar cellFour-terminal perovskite/CIGS double-junction tandem solar cell:Firstly,the optimal thickness of perovskite and CIGS layer is 600 nm and 3.6μm respectively,the initial PCE is 22.7%.Then,PCBM layer thickness is reduced to decrease the parasitic absorption.And the PCE is improved to 25.7%when PCBM layer thickness is 20 nm.After that,Mg F₂,acting as the optimal antireflection material among Mg F₂,SiO₂ and Al₂O₃,can improve PCE from 25.7%to 27.9%.Furthermore,comprehensive consideration of the relationship between the resistivity and light transmittance of the FTO layer,the PCE can be further improved to 31.0%.Two-terminal perovskite/CIGS double-junction tandem solar cell:Firstly,the optimal PCE with 30.8%can be obtained under the condition of current-matching.In addition,results showed that to enhance the device performance,the quality of perovskite films should be improved by enlarging the grain size to decrease the trap states at grain boundary,and the grapheme electrode should is 10 nm,3.Anisotropy effect of CH₃NH₃PbI₃and CsPbI_xBr_3-xcrystalThe results obtained from first-principle theory indicate that tetragonal CH₃NH₃PbI₃,CsPbI₂Br,and CsPbIBr₂ are anisotropic,CsPbI₃and CsPbBr₃ are isotropic.In addition,the carrier mobility and absorption coefficient of tetragonal CH₃NH₃PbI₃,CsPbI₂Br and CsPbIBr₂ along[001]orientation are superior to that along[100]orientation.Furthermore,in the device level,the solar cell and photodetector based on tetragonal CH₃NH₃PbI₃,CsPbI₂Br and CsPbIBr₂ along[001]orientation are superior to that along[100]orientation as well.Therefore,the[001]orientation should be selected for tetragonal CH₃NH₃PbI₃,CsPbI₂Br and CsPbIBr₂ single crystal in the practical device applications.4.The optoelectronic application of new vacancy-ordered double perovskiteThe band gap of new vacancy-ordered double perovskite Cs₂CrI₆and Cs₂TiI₆ is 1.08 eV and 1.02 eV,respectively,which is suitable to applied in solar cell.In addition,the excellent absorption coefficient of Cs₂CrI₆and Cs₂TiI₆ suggests that solar cell based on Cs₂CrI₆and Cs₂TiI₆is able to capture most number of photons,the high carrier mobility of Cs₂CrI₆（μ_n=7.24×10³ cm²/（V·s）,μ_p=6.57×10³ cm²/（V·s））and Cs₂TiI₆（μ_n=2.2×10³cm²/（V·s）,μ_p=7.3×10³ cm²/（V·s））indicates that few carriers will be captured by traps.Therefore,the PCE of Cs₂CrI₆single-junction solar cell and Cs₂CrI₆/CH₃NH₃PbI₃double-junction tandem solar cell can be up to 22.4%and 26.6%,respectively.Similarly,the PCE of Cs₂TiI₆single-junction solar cell and Cs₂TiI₆/CH₃NH₃PbI₃ double-junction tandem solar cell can be up to 22.7%and 26.8%respectively,and is able to withstand ultrahigh fluence proton beam up to 10¹³ p.cm^-2.