Optimization of an inverted organic solar cell

An inverted organic solar cell, consisting of an ultrathin Ca layer for electron transport, the blend of poly(3-hexylthiophene) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C61 for photon absorption, and a MoO3 layer for hole transport, is optimized. The insertion of MoO3 layer between photoactive layer and Ag anode has been demonstrated to improve both the photocurrent and the fill factor. By optical modeling and experiment, we find that the MoO3 layer also functions as an optical spacer for thin devices. For the optimized device with an active layer thickness of 85 nm, Ca thickness of 0.5 nm, and MoO3 layer thickness of 5 nm, a maximum power conversion efficiency of 3.86% was achieved.