High Efficiency Solar Cell Based On The Control Of Perovskite Crystallization Process

In recent years,the rapid development of perovskite solar cells has attracted much attention from both fields of science and industry.In order to promote its industrialization process,researchers have focused on various ways further to improve the performance of solar cell device,in which the preparation of the perovskite active layer as the most critical part has received considerable attention.Excellent quality of perovskite film is the basis of ensuring high efficiency perovskite devices.In this thesis,we used anti-solvent process,additive engineering and interface engineering,to control the perovskite crystallization rate,thereby adjust the perovskite layer morphology and ultimately promote the performance of perovskite solar cells.It can be divided into the following three parts:（1）Add dimethyl sulfoxide（DMSO）to the perovskite precursor solution to control the morphology of the perovskite film;although the use of anti-solvent washing during the one-step solution deposition process of perovskite film can alleviate the shortcomings caused by too fast the crystallization,such as low film coverage and full of defects,the repeatability of anti-solvent washing is poor.The anti-solvent free one-step solution perovskite thin film deposition technology with lead acetate（Pb（Ac）₂）as the single lead source avoids the uncontrollable factors brought by the anti-solvent washing process and improves the repeatability of the device,but its device efficiency needs to be improved.Regarding this,we added a small amount of DMSO into the perovskite precursor solution to control of the perovskite film morphology.The experimental results show that the addition of DMSO will cause the formation of perovskite mesophase,slow down the crystallization rate of perovskite duiring the spin-coating process,and thus form a perovskite film with more uniform and dense grains and smooth surface.The quality of the perovskite film increased with the increase of the DMSO ratio and then decreased.With the addition of 3%DMSO,the power conversion efficiency increased by 18%compared with the control device.（2）（FA）_y（MA）_1-yPbBr_xI_3-x mixed cationic halogen-doped perovskite structure;although the most common organic-inorganic hybrid perovskite material MAPbI₃ shows excellent photoelectric properties in many aspects.The use of mixed cations and halogen doping can further improve the light absorption,charge carrier transport and stability of the device.For the deposition of mixed cation perovskite material,the timing of anti-solvent washing during the spin-coating of the perovskite precursor solution was optimized.The experimental results show that when anti-solvent is added at6-8 s from the beginning of spin-coating,a smooth perovskite film is obtained.The corresponding perovskite solar cell has a Voc of 0.93 V,a Jsc of 19.10 m A/cm²,a FF 74.97%,and a PCE is 13.27%.In addition,a high-quality perovskite film is obtained based on a dual lead source system including Pb（Ac）₂ and PbI₂ by using one-step anti-solvent free solution proces techonlogy.Efficient perovskite solar cell with a Voc of 1.05 V,a Jsc of 19.64 m A/cm²,a FF of 71.17%and a PCE of 14.63%is obtained.Furthermore,the device performance has been improved by modifying the surface of perovskite with Br Ac with a Voc of 1.05 V,a Jsc of 21.91 m A/cm²,a FF of 72.18%and a PCE of16.59%.（3）All-inorganic perovskite solar cell based on CsPbI₂Br.Although the organic-inorganic hybrid solar cell has achieved a comparative light conversion efficiency value to that of a commercial silicon-based solar cell,its poor stability in the air hinders its industrialization process.Full-inorganic perovskite materials have more stable physical and chemical properties,which make it possible to achieve highly stable and efficient perovskite solar cells.However,now it suffers from relatively low device performance.In this thesis,a graded thermal annealing on the spin-coating film in combination with DIO additive in the precursor solution are used to control the crystallization process of perovskite.Experimental results show that perovskite phase is formed at relatively low temperature with graded thermal annealing procee.Although DIO can slow down the crystallization process of perovskite,it has little effect on the device performance.In addition,by improving the interface contact between PTAA and the perovskite active layer,all-inorganic PSCs with more excellent properties are obtained.The experimental results show that the surface of PTAA modified with Al₂O₃ nanoparticles improves the wettability of the perovskite precursor solution on the surface of PTAA and improves the coverage of perovskite on PTAA,thereby obtaining highly efficient all-inorganic PSCs.The optimal device using Al₂O₃ interface layer Voc is 0.96 V,Jsc is 13.18 m A/cm²,FF is 66.89%,PCE is 8.43%.Compared with the standard device,performance parameters have been improved.