Inverted tandem organic solar cells with a MoO3/Ag/Al/Ca intermediate layer

An inverted tandem organic solar cell, consisting of two bulk heterojunction subcells with identical poly(3-hexylthiophene) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C61 active layer, and an intermediate layer made of ultrathin multiple metal layers of Ca/Al/Ag and metal oxide MoO3, is reported. This intermediate layer is of advantage in high transparency and low series resistance. Moreover, it serves as the charge recombination center effectively, and renders an exact summation of the open-circuit voltages (1.18 V) of the two subcells and a high fill factor (61.8%). The maximum power conversion efficiency obtained is 2.78% under simulated 100 mW/cm2 [air mass (AM) 1.5G] solar irradiation, comparable to those of the two subcells.