Optimal Design And Preparation Of Planar Heterojunction Perovskite Solar Cells

At present,development of new energy and protection of environment have been widely concerned.Among numerous technologies of new energy,it is considered that solar photovoltaic technology is a feasible method to solve the energy issue.Currently,perovskite materials have been widely studied in the field of photoelectric devices due to some advantages such as high light absorption capacity,high carrier migration rate,adjustable band gap,and so on.The perovskite solar cells have become the research focus in the field of solar cells because of the superiorities of high photoelectric conversion efficiency and simple preparation method.Within many structures of perovskite solar cells,planar heterojunction cells have become an important research content due to the advantages of simple structure and preparation method.However,some problems such as low interfacial wetting property and few charge carrier separation interface still exist in planar perovskite solar cells.According to these problems,this thesis mainly focuses on the preparation of electron transport layer and perovskite materials with high qualities in air atmosphere.In addition,the projects of improving the performance of perovskite solar cells by introducing interfacial modifying layer of ultrathin mesoporous TiO2 and LSPR effect of Au nanoparticles are detailed studied.The main research contents and results of this thesis are as follows:(1)Optimization of preparation method of perovskite materials.The preparation technology of TiO2 electron transport layer and perovskite material by using spin coating method with the purpose of fabricating solar cell with high performance is explored.Firstly,compact TiO2 layer is fabricated by spin coating method.The effect of spin coating atmosphere and deposition time of precursor solution on the morphology of TiO2 compact film is explored.It is found that in a closed environment and with the deposition time of 30 s,compact TiO2 layer with the best morphology can be synthesized which is fit for being applied in planar perovskite solar cells.Further,effect of TiO2 substrate,dosage of DMSO additive,method of annealing,and annealing temperature on the morphology of perovskite films are studied.The results indicate that increasing the surface roughness of TiO2 is benefit for improving the quality of perovskite material;the surface morphology of perovskite material is the best when the molar ratio of DMSO and PbI2 is 3:1;effect of direct annealing on the morphology of perovskite material can be eliminated by the method of indirect annealing;the annealing temperature of 100℃ is the optimal one.This work provides guidance on the preparation of electron transport layer and perovskite material with high quality in air atmosphere.(2)Ultra-thin mesoporous perovskite solar cells.The planar heterojunction perovskite solar cell with an interfacial modifying layer of ultrathin mesoporous TiO2 is fabricated and investigated.In this experiment,an interfacial modifying layer of ultrathin mesoporous TiO2 is introduced basing on the technology of interfacial engineering and thus the planar cell with high performance is fabricated.Firstly,preparation method of ultrathin mesoporous TiO2 is optimized.The effect of the concentration of precursor solution and the speed of spin coating on the morphology of ultrathin mesoporous TiO2 is explored.The results indicate that ultrathin mesoporous TiO2 with ideal surface and section morphology can be fabricated on the surface of compact TiO2 when the concentration of precursor solution is 1:20 and the speed of spin coating is 2000 rpm,respectively.Furthermore,it is found that compared with traditional planar and mesoporous perovskite solar cell,the interfacial modifying layer of ultrathin mesoporous TiO2 is benefit for the growth of perovskite grain and compactness.An average photoelectric conversion efficiency of 18.5%is achieved which is 1～2%higher than that of traditional planar and mesoporous cell,and meanwhile,the hysteresis coefficient as low as 4.5%is also achieved.By the study of internal mechanism,this kind of ultrathin mesoporous perovskite solar cell integrates the advantages of planar and mesoporous cell.On the one hand,it possesses the properties of the high quality of perovskite and a high electron transport capacity in planar cell;on the other hand,high carrier separation efficiency in mesoporous cell can also be maintained.This work provides information on the optimal structure design and preparation of high-performance solar cells.(3)Performance enhancement of perovskite solar cells by localized surface plasmon resonance.In this work,Au nanoparticles are introduced as an insert layer between FTO and SnO2 compact layer,and the effect of Au nanoparticles on the performance of perovskite solar cell is detailed investigated.Firstly,preparation technology of SnO2 and Au nanoparticles is optimized.The results show that when the concentration of SnO2 precursor solution is 0.3 mol/L,the morphology of SnO2 and quality of perovskite material is the best.Au nanoparticles with well-distributed morphology can be fabricated by depositing the thickness of 2 nm Au film and then being rapid annealed at 400℃.The LSPR peak of the Au nanoparticles is located at about 555 nm.The photoelectric conversion efficiency of perovskite solar cell is improved greatly with the help of Au nanoparticles,which is increasing from 16.61%to 18.77%.Analyzing from different characterizations,it is found that LSPR of Au nanoparticles can not only improve the light absorption of the cell,but also enhance the carrier separation efficiency.Thus,the performance of this kind of perovskite solar cell is improved greatly.This work provides guidance on the structure design and preparation of new-style and high-efficiency solar cells.