Aqueous Photoelectrochemical Reduction of Anthraquinone Disulfonate at Organic Polymer Films

Abstract

The photoelectrochemistry (PEC) of poly(3‐hexylthiophene) (P3HT) is investigated by studying the photocathodic reduction of anthraquinone‐2,7‐disulfonate (AQ27DS). A photocurrent of ≈ 100 μA cm −2 is obtained using ≈ 5 × 10 −3 m AQ27DS and 100 mW cm −2 visible light. The photon‐to current‐efficiency approaches ≈ 1% when irradiated with low intensity monochromatic light. The photoreduction proceeds by either a 2‐electron, 2‐proton, or 2‐electron, 1‐proton process depending on the solution pH. The band energy levels of P3HT shift by ≈ 150 mV in contact with aqueous solutions over a 1–12 pH range, and considerable more in the presence of AQ27DS during PEC, to the extent that Fermi level pinning occurs. This work reveals that the efficiency of electron–hole separation is required to improve photoefficiency and the interaction of redox couples with the P3HT semiconductor interface is warranted in order to understand the photovoltages developed across the semiconductor/electrolyte interfaces. image