Preparation Of Nickel Oxide Nanoparticles And Their Application In Perovskite Solar Cells

With the vigorous development of perovskite solar cells（PSCs）,it has gradually become one of the most valuable research directions in the field of photovoltaics.Up to now,the certified power conversion efficiency（PCE）of PSCs has reached 25.7%.However,due to the instability of the material,the photovoltaic performance of PSCs is easily affected by the environment,which seriously hinders its potential for large-scale promotion.As an excellent p-type semiconductor,nickel oxide（NiO_x）is widely used to fabricate hole transport layer（HTL）in PSCs due to its large band gap（>3.5 e V）,good energy level alignment and excellent stability.However,the poor quality of NiO_x nanoparticles and agglomeration in solvents limit the photoelectric performance of NiO_x-based PSCs.Therefore,this paper studies the preparation and dispersion process of NiO_x nanoparticles and applies them to PSCs with different structures.The main research contents are as follows:NiO_x nanoparticles were prepared by chemical precipitation method using Ni（NO₃）₂·6H₂O as nickel source.The particle size of the product was controlled by introducing sodium dodecyl sulfate（SDS）into the reaction solution.The main influencing factors such as nickel nitrate concentration,precipitant concentration,reaction system p H,SDS content and reaction solvent were investigated.The reaction conditions were further optimized by response surface experiments.Finally,the preparation of hydrophilic NiO_xnanoparticles with small particle size（about 6 nm）and uniformity was achieved.Aiming at the problem that NiO_x nanoparticles prepared by chemical precipitation method are easy to reunite in water,this paper proposes a strategy of introducing sodium hexametaphosphate（SHMP）to improve the stability of NiO_x-water dispersion system.At the same time,the stability of NiO_x-nonpolar dispersion was improved by adding oleylamine（OLA）to NiO_x-chlorobenzene dispersion.In addition,vinyltriethoxysilane（VTES）was used to chemically modify NiO_x nanoparticles to make them stably dispersed in non-polar solvents,laying a foundation for the application of NiO_x nanoparticles in formal PSCs.The NiO_x-water dispersion containing SHMP was used to fabricate the HTL.The results showed that the NiO_x-SHMP film had a denser and smoother film morphology without loss of photoelectric properties,which was beneficial to improve the crystal quality and light absorption ability of the perovskite layer and reduced the defect state density of the perovskite film.The PCE of the inverted device based on NiO_x-SHMP film could reach18.73%.The unencapsulated device could maintain an initial efficiency of about 90%after being stored in air at 25°C and relative humidity of 30±5%for 500 h.In addition,NiO_x-chlorobenzene dispersion containing OLA and NiO_x nanoparticles modified by VTES were used to fabricate formal devices,respectively.The results showed that both NiO_x-OLA and NiO_x-VTES had good film quality,but the introduction of long-chain ligands would cause a decrease in the conductivity of the film.The PCE of the devices based on NiO_x-OLA and NiO_x-VTES were 10.32%and 13.78%,respectively.The unencapsulated devices could maintain more than 90%initial efficiency after being stored in air for 500 h.