Rheological Behavior And Film Forming Characteristics Of Inks For Gravure Printing Organic Solar Cells

Organic solar cells(OSCs)have received extensive attention due to their unique advantages of flexible,lightweight,non-toxic,low-cost,and large-area printing fabrication-compatible,as well as their huge application potential in building photovoltaics,indoor photovoltaics,wearable electronics and portable energy.However,the large-area preparation method of OSCs still has some problems,such as low resolution of deposition patterns and inability to be two-dimensional patterned,which makes the module geometric filling factor(GFF)of OSCs low and poor aesthetics,thus hindering the industrialization of organic solar cells.Gravure printing is a roll-to-roll large-area preparation method with two-dimensional patterning.It can prepare twodimensional patterns with sharp edges,which is expected to improve the GFF and aesthetics of modules.The balance between rheological properties of inks and photoelectric properties of films is a key scientific problem in the preparation of gravure printing OSCs.Aiming at this key problem,this paper studied the balance method between rheological properties of OSC inks with different dimensions nanomaterials and photoelectric properties of films,as well as the relationship between rheological properties of ink and film forming properties.Large-area uniform OSC film was prepared by gravure printing,which realized the high efficiency OSCs preparation.The main research results are as follows:1.The surface tension and viscosity of silver nanowire(AgNW)inks were well regulated by mixing solvents and adjusting the concentration.The AgNW films with large-area uniform,patterning and excellent photoelectric properties were prepared by gravure printing.The effect of rheological properties of AgNW ink on the quality of gravure-printed film is studied systematically.It was found that inks with lower surface tension were better wettable on the substrate,and excellent wettability was a prerequisite for the preparation of high-quality film in gravure printing.The fluidity of one-dimensional AgNW with high aspect ratio can be significantly improved by appropriate ink viscosity,thus improving the uniformity of AgNW films.The relationship between rheological properties and film forming properties of onedimensional nanomaterial inks was established.Finally,the highest power conversion efficiency(PCE)of 13.61%(certified efficiency of 12.88%)is achieved for 1 cm2 OSCs based on the gravure-printed AgNW films.2.The viscosity and volatilization rate of zinc oxide(ZnO)inks were well regulated by the method of introducing polyvinyl pyrrolidone(PVP)and combining with the mixed solvent.The large-area uniform and excellent photoelectric performance ZnO:PVP films were prepared by gravure printing.The effect of rheological properties of ZnO inks on the quality of gravure-printed films is systematically studied.It is found that the volatilization rate of ink is the main factor affecting the macrohomogeneity of gravure-printed ZnO films.The introduction of PVP can improve the viscosity of ZnO ink and enhance the interaction between ZnO and AgNW,thus improving the microscopic compactness of ZnO films.The relationship between rheological properties and film forming properties of zero-dimensional nanomaterial inks was established.Finally,the highest PCE of 17.07%is achieved for 1 cm2 OSCs based on the gravure-printed PET/AgNW/ZnO:PVP films.3.By adjusting the molecular weight of polymer and mixing solvent,the viscosity and volatilization rate of the active layer inks were well regulated,and the active layer films with large-area uniform and excellent performance was prepared by gravure printing.The method of polymer molecular mass control not only effectively regulates the viscosity of the active layer ink,but also avoids the degradation of device performance due to the introduction of other components.The effect of rheological properties of active layer ink on the quality of gravure-printed film was systematically studied.It was found that the viscosity of ink was the main factor affecting the quality of gravure-printed film,and the appropriate viscosity of ink can eliminate the random stripe of active layer films.The relationship between rheological properties and film forming properties of real solution inks was established.A new strategy is proposed to inhibit the aggregation of active layer films by increasing the viscosity of ink.Finally,OSCs with full gravure printing(three layers)were prepared,and the PCE of 14.45%was obtained.