Efficient organic solar cells with polyfluorene derivatives as a cathode interfacial layer

Use of a polyfluorene derivative (WPF-oxy-F) as the cathode interfacial layer was investigated for low-cost and high-efficiency organic solar cells (OSCs) based on poly(3-hexylthiophene) (P3HT) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C61 (PCBM). Insertion of the WPF-oxy-F interfacial layer between the P3HT/PCBM active layer and the metal cathode increased overall power conversion efficiency from 2.95% to 3.77% primarily due to the improved open circuit voltage and enhanced fill factor, resulting from a reduction of the metal work-function through the introduction of WPF-oxy-F.