Blade Coating of Alloy as Top Electrodes for Efficient All-Printed Organic Photovoltaics

All printing of organic photovoltaics (OPVs) including the top electrode is highly desirable for achieving cost-effective, high-throughput, and large-area photovoltaic manufacturing. Here, the printing of a low-melting-point alloy as top electrodes in OPVs via blade coating is investigated. The Field's metal (FM) with the melting point of 62 degrees C is adopted for the top electrodes, because FM can be printed under moderate temperatures without harming the active layers while remaining solid state under solar irradiation. The correlations between the processing parameters and properties of the blade-coated electrodes are elucidated. OPVs based on the D18:Y6 active layer and blade-coated FM electrodes achieve a highest power conversion efficiency of 17.28%. The OPVs with FM-electrode demonstrate much higher thermal stability than that of the Ag-electrode devices. All-printed OPVs, in which the FM electrode is blade coated and the other layers are prepared by flexible micro-comb printing, exhibit an efficiency of 16.07%. The results represent the records of evaporation-free and all-printed OPVs, demonstrating that printing FM as OPV electrodes is a cost-effective and time-saving strategy to substitute the vacuum-evaporated metals, as well as a feasible route toward high-performance all-printed OPVs.