Visible Light Photocatalyst Prepared from Active Organic Photovoltaic Cell

The organic photovoltaic devices (OPVs) have potential in low-cost, large-area printing routes with high efficiency owing to the variety of organic materials. The active layer has a role to absorb photon and convert to electrostatic energy of separated electron and hole pair. If the separated charge in its active layer can be utilized to chemical reaction directly without collecting by electrodes, it would be a simple device for photoenergy conversion and has a great merit to use the photon energy. Here we introduce an large negative threshold potential of −0.35 V vs. Ag/AgCl by the use of ZnPc/PCBM:P3HT/ZnO electrode, which was prepared by removing PEDOT:PSS/Au electrode of an inverted OPV device [1] and coating with ZnPc. A co-photocatalysis property of ZnPc was observed in the photoelectrochemistry and scanning Kelvin probe microscopy.From the mother OPV, the gold electrode was removed mechanically and ZnPc was coated by vapor deposition. The detailed experimental conditions and characterizations of the electrode are shown in Ref [2].Fig. shows voltammograms in a thiol solution for the BHJ electrode (a) and the ZnPc coated BHJ electrode (b). The photoanodic current (red) for the electrode with ZnPc (b) was much larger than that without ZnPc (a). For the ZnPc coated BHJ electrode with ZnO, the threshold potential of the photoanodic current was around −0.35 V vs. Ag/AgCl. On the other hand, for the ZnPc coated BHJ electrode without ZnO, the threshold potential of the photoanodic current was around −0.0 V vs. Ag/AgCl as shown in our previous paper [3]. The present larger gain than that without ZnO would be due to the effect of ZnO as a hole blocking layer. The threshold value of −0.35 V vs. Ag/AgCl was almost equal to the conduction band edge potential of ZnO, that is, the photogenerated electrons in the BHJ active layer can preferentially transfer to ZnO when the anodic polarization of ITO was deeper than the ZnO edge. Note that the ZnPc electrode exhibited an anodic current in the dark with the threshold potential of +0.25 V vs. Ag/AgCl, that is, the ZnPc can function as a catalyst of 2-mercaptoethanol oxidation. The large anodic photocurrent may be caused by such a catalytic function of ZnPc.References T. Kuwabara, et al., Sol. Energy Mater. Sol. Cells, 2008, 92, 1476.K. Nagai, et al., Chem. Commun. 2019, 55, 12491.T. Abe, et al. Chem. Phys. Lett., 2012, 549, 77.M.-F. Ahmad, et al. NPG Asia Mater., 2018, 10, 630.Figure 1