Synthesis Of Novel Inorganic Hole Transport Materials And Their Application In Perovskite Solar Cells

In recent years,inorganic-organic metal halide perovskite solar cells?PSCs?have attracted wide attentions due to their rapid development of high efficiency and low cost,which is a promising next generation solar cell technology.Hole transport materials?HTMs?and electron transport layer materials?ETLs?are key components of PSCs due to the need for charge collection selectivity.Hole transport materials?HTMs?play a vital role in effective charge extraction,thereby achieving higher overall efficiency.Therefore,finding an efficient,stable,and low-cost hole transport layer material in PSCs has always been one of the research hotspots in this field.At present,organic small molecules including 2,2',7,7'-Tetra[N,N-bis?4-methoxyphenyl?amino]-9,9'-spirodifluorene?spiro-OMe TAD?and poly(bis?4-phenyl??2,4,6?trimethylphenyl?amine??PTAA?are the most widely used organic hole transport materials.However,their complicated synthesis and purification process limit the application.In addition,the introduction of dopants in organic hole transport will affect the lo ng-term stability of the device.Therefore,the use of organic hole transport materials may become a potential obstacle to the industrial development of perovskite solar cells,so it is necessary to find new inorganic hole transport materials with low pric e and stable properties.This thesis mainly studies the application of new inorganic hole transport materials for perovskite solar cells,and the research contents are carried out as follows.?1?Two-dimensional lamellar NiO array s with controllable sizes are constructed on the surface of conductive glass for the hole transport layer of inverted perovskite solar cells.NiO with two-dimensional lamellar structure is synthesized by solvothermal method with nickel acetate as nickel source,urea as mineralizer and ethanol as solvent.By adjusting the reaction time,two-dimensional lamellar NiO arrays of different sizes are synthesized.It is found that with the increase of reaction time,the size of two-dimensional lamellar NiO array increases gradually.The dim ensions of the obtained two-dimensional lamellar NiO arrays are 200 nm,400 nm and 600 nm respectively.Using scanning electron microscopy?SEM?to observe the surface of NiO with two-dimensional lamellar structure,it can be found that the lamellar arrays are formed by the directional aggregation of nanocrystalline small particles.When the two-dimensional lamellar NiO of different dimensions are applied as the hole transport layer of perovskite solar cells,the highest efficiencies of the devices are 9.0%,12.2% and 14.3% respectively.The efficiency of the devices increases with the decrease of the size of the two-dimensional lamellar NiO array,mainly because the increase in the size of the two-dimensional lamellar NiO array results in a decrease in ligh t transmittance and hole transport performance.?2?Crystalline CoO nanoparticles are synthesized and used as h ole transport layer materials for inverted perovskite solar cells.Cobalt acetylacetone is used as the cobalt source and olamine as the solvent t o synthesize CoO nanoparticles under the protection of argon by the oil bath method.The particle size could be controlled as small as 10 nm.The long carbon chain of oleamine on the surface of CoO nanoparticles can be removed through ligand exchange,whic h transformed the surface of CoO film from hydrophobic to hydrophilic and promoted the growth of perovskite film.The contact angle test shows that the film after ligand exchange has a smaller contact angle than the film before ligand exchange.UV-vis spectroscopy tests show that in the wavelength range of 400-800 nm,linear scanning voltammetry shows that the membrane conductivity after ligand exchange is higher than before.Using the ligand-exchanged film and the non-ligand-exchanged film used in the devi ce,10.1% and 2.2% of the power conversion efficiencies are obtained.As the cell efficiency increases after ligand exchange,this is mainly because the ligand exchange improves the conductivity of the CoO film,improves the hydrophilicity of the film,and reduces the resistance to increase the carrier transmission efficiency.?3?AgCuO₂ nanoparticles with controllable size s are in-situ fabricated on the surface of conductive glass and used as hole transport layer materials for inverted perovskite solar cel ls.With silver nitrate as the silver source and copper nitrate trihydrate as the copper source,ammonia water as the complexing agent and to adjust a strong base solution,AgCuO₂ nanoparticles are grown on the ITO conductive glass by electrodeposition.By adjusting the electrodeposition time,nanoparticles with length of 150-300 nm and width of50-100 nm can be obtained.Films of different sizes are obtained according to the electrodeposition time,and the transmittance will gradually decrease as the film thickness increase.Thin films with deposition times of 30 s,45 s,and 60 s are applied to devices and assembled into perovskite solar cells.The measured power conversion efficiencies of the devices are 4.4%,7.3%,and 9.6%.The PCE increases with the de crease in the size of Ag Cu O ₂,mainly due to the reduction in the thickness of the film,which improves the light transmission rate and improves the hole transport performance.