Study On Film Formation Process Of Perovskite Absorbing Layer Based On Solvent Effect

Organic-inorganic hybrid halide perovskite material has excellent photoelectric properties,such as high absorbance,long carrier transport distance,lower exciton binding energy,and bipolar transport as well.At present,the certified efficiency of perovskite solar cell has reached to 24.2%.For these kinds of devices,the fabrication of the perovskite laye significantly influences its grain size,crystallinity,and coverage,which ultimately determines the electrical parameters,such as fill factor,short-circuit current,open circuit voltage and power conversion efficiency(PCE)of perovskite solar cells.In order to optimize the microstructure of perovskite layer,the nucleation and grain growth of crystal require to be controlled during deposition process.Anti-solvent extraction will lead to fast nucleation,thereby increasing the crystalline degree of perovskite layer.In this thesis,the solvent effect on process of perovskite layer is investigated Primarily,solvent atmosphere annealing is introduced to control the grain growth direction and grain size of the perovskite crystal,thereby obtaining a perovskite layer with good crystallinity and high coverage.Secondly,the multi-component anti-solvent is applied to treat the perovskite layer,aiming at the uniformity of grain size to optimize the opto-electrical performance of perovskite layer.We have found that:Ethyl acetate(EA),mixed with a good solvent can effectively drive residual good solvent from perovskite layer during spin-coating process,which will promote perovskite recrystallization and effectively increase the average perovskite grain size of perovskite to 500 nm.In additon,solvent atmosphere can lead to the rearrangement of perovskite crystal.In this way,intergranular arrangement becomes tightened,and there is no void in perovskite layer.The PCE of perovskite solar cell is increased to be 15.33%,and fill factor(FF)reaches to 71%.Furthemore,compared with the solvents,such as chlorobenzene(CB),diethyl ether(DE)and toluene(TL),the non-toxic ethyl acetate and n-propanol can further improve the coverage and compactness of perovskite layer.Varying the proportion of n-propanol in the anti-solvent mixture,the the perovskite grain size can be well-controlled.Results show that,with the ratio of ethyl acetate and n-propanol reaching to 70:30,the grain size gets most uniform,and the PCE of fabricated device rises up to 15.88%while the hysteresis coefficient is below 0.06.