Simple Sn-based coordination complex as cathode interlayer for efficient organic solar cells

Cathode interlayer (CIL) is responsible for electron extraction and hole blocking between the photoactive layer and the electrode. Since the excellent inorganic CIL materials, such as ZnO, TiO2 and SnO2, are difficult to be applied in high performance non-fullerene organic solar cells with conventional structures, novel organic-inorganic hybrid materials have attracted much attention recently, owing to their advantages from both organic and inorganic CIL materials. Herein, we reported that the commercial Sn-based coordination complex, Sn(acac)2 and BuSnOOH could be employed as excellent CIL in both PM6:BTP-4Cl and PM6:IT-4F based OSCs. Because of the better aligned energy levels, smooth film on the active layer and higher electron mobility, BuSnOOH based device was able to facilitate more efficient charge extraction and reduce charge recombination. As a result, an impressive PCE of 17% was obtained for OSCs with the ITO/PEDOT:PSS/PM6:BTP-4Cl/BuSnOOH/Ag structure, while the corresponding OSC with Sn(acac)2 as CIL displayed moderate PCE of 15.57%.