Metal oxide-free flexible organic solar cells with 0.1 M perchloric acid sprayed polymeric anodes

Abstract

Future flexible organic solar cells (OSCs) require high efficiency, good flexibility and low fabrication cost. Here, we demonstrate a metal oxide-free flexible OSC based on poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) anodes with a small amount of perchloric acid (HClO₄) spray doping. The optimized flexible OSCs yield a mean efficiency of 16.44%, which is the highest value for metal oxide-free flexible OSCs reported so far. The high efficiency is ascribed to the HClO₄ spray doping that pulls the anode's Fermi level down, decreases the sheet resistances, and induces an intimate contact at interfaces. The spray doping also avoids direct contact between HClO₄ and plastic substrates, and thus the devices maintain good flexibility. This work clearly demonstrates the advantage of the unique HClO₄ spray doping method over the well-known strong acid soaking method and complicated transfer-printing strategies for application in anodes of flexible OSCs.