A thickness-insensitive cathode interlayer （CIL） is necessary for large-area polymer solar cells （PSCs）, in which thickness variation is unavoidable. These C1L materials are typically based on n-type conjugated po...A thickness-insensitive cathode interlayer （CIL） is necessary for large-area polymer solar cells （PSCs）, in which thickness variation is unavoidable. These C1L materials are typically based on n-type conjugated polymer/molecule backbones, which show strong light absorption in the visible/near-infrared （NIR） region. This interferes with the sunlight absorption by the active layer and deteriorates device efficiency. In this study, we developed graphene quantum dots functionalized with ammonium iodide （GQD-NI） at the edge as a thickness-insensitive CIL with high optical transparency. The peripheral ammonium iodide groups of GQD-NI formed the desired interfacial dipole with the cathode to decrease the work function. The graphene basal planes of GQD-NI with a lateral size of ca. 3 nm demonstrated a good conductivity of 3.56 ×10-6 S.cm-1 and high transparency in the visible/NIR region （λmax abs = 228 nm）. Moreover, GQD-NI was readily soluble in polar organic solvents, e.g., methanol, which enabled multilayer device fabrication with orthogonal solvent processing. As a result, the PSC device with GQD-NI as the CIL exhibited a power conversion efficiency （PCE） of 7.49%, which was much higher than that of the device without the CIL （PCE = 5.38%） or with calcium as the CIL （PCE = 6.72%）. Moreover, the PSC device performance of GQD-NI was insensitive to the GQD-NI layer thickness in the range of 2-22 nm. These results indicate that GQD-NI is a very promising material for application as a CIL in large-area printed PSCs.展开更多
文摘A thickness-insensitive cathode interlayer （CIL） is necessary for large-area polymer solar cells （PSCs）, in which thickness variation is unavoidable. These C1L materials are typically based on n-type conjugated polymer/molecule backbones, which show strong light absorption in the visible/near-infrared （NIR） region. This interferes with the sunlight absorption by the active layer and deteriorates device efficiency. In this study, we developed graphene quantum dots functionalized with ammonium iodide （GQD-NI） at the edge as a thickness-insensitive CIL with high optical transparency. The peripheral ammonium iodide groups of GQD-NI formed the desired interfacial dipole with the cathode to decrease the work function. The graphene basal planes of GQD-NI with a lateral size of ca. 3 nm demonstrated a good conductivity of 3.56 ×10-6 S.cm-1 and high transparency in the visible/NIR region （λmax abs = 228 nm）. Moreover, GQD-NI was readily soluble in polar organic solvents, e.g., methanol, which enabled multilayer device fabrication with orthogonal solvent processing. As a result, the PSC device with GQD-NI as the CIL exhibited a power conversion efficiency （PCE） of 7.49%, which was much higher than that of the device without the CIL （PCE = 5.38%） or with calcium as the CIL （PCE = 6.72%）. Moreover, the PSC device performance of GQD-NI was insensitive to the GQD-NI layer thickness in the range of 2-22 nm. These results indicate that GQD-NI is a very promising material for application as a CIL in large-area printed PSCs.
