Research On Anti-solvent Interface Engineering Of Perovskite Crystals And Its High Efficiency Solar Cells

Solar cells with CH₃NH₃PbI₃ type perovskite films as active layer are increasingly considered as a crucial research direction in renewable energy field in the past decade,and the highest certified power conversion efficiency（PCE）of 25.2%has been achieved for perovskite solar cells（PSCs）,and the quality of perovskite active layer is the key factor affecting the performance of the PSCs.Controlling the grain growth process to obtain perovskite films with high crystallinity,large size grains,few grain boundaries,low trap density and carrier recombination rate has become one of the current research hotspots.Treating different status of perovskite film in anti-solvent atmosphere to explore the effect of anti-solvent atmosphere on perovskite films.The film fabrication process is optimized based on experimental phenomena and device performance data,and n-Hexane,ethyl acetate（EAC）and toluene are successively introduced for perovskite film vapor annealing.X-Ray Diffraction（XRD）and UV-visible are used to determine the best induction volume,scanning electron microscopy（SEM）and atomic force microscopy are used to analyze the surface morphology of annealed perovskite films with different solvents.Combining film characterization data,solvent physical and chemical properties and device performance,it is proposed that anti-solvent annealing could improve film quality,and with the increase of the boiling point of the anti-solvent introduced,the promotion of film quality is gradually enhanced,and device performance is also improved.In order to further explore the mechanism of anti-solvent annealing and improve device performance,o-dichlorobenzene（o-Ph Cl₂）and chlorobenzene（Ph Cl）with higher boiling points are selected for film annealing.A closed annealing environment is construct to calculate the vapor pressure of anti-solvent,and qualitatively analyze the relationship between vapor pressure and film quality.The anti-solvent vapor reaches saturated pressure when the introduced volume is 10（o-Ph Cl₂）and 40μL（Ph Cl）,which performed the strongest promotion effect on film quality.The effect of anti-solvent molecule on the phase transformation,morphology evolution of perovskite film is systematically investigated by XRD and SEM,which proves to inhibit the solvent evaporation of the film,promote the crystallites dissolution and ordered secondary growth on the surface of large grains under the synergy of temperature,to obtain the film with high crystallinity,large grain size and low defect density.Moreover,PCE of the optimized device with the secondary growth perovskite film induced by o-Ph Cl₂and Ph Cl is 20.72%and 19.49%.Under indoor natural environment aging for 2400 h at 45±5%relative humidity,the efficiency of the device maintained above 85%and78%of initial value,while the untreated device only maintains about 35%of the original efficiency.