Increasing Electrode Work Function Using a Natural Molecule

Abstract

Abstract Providing sustainability to organic electronics is highly demanded to reduce the negative impact of organic devices on environments and human health upon their disposal. To attain biodegradability and biocompatibility of the electronic devices, utilization of the natural molecules for the device constituents is essential. In this study, it is reported that the adsorption of caffeic acid (CfA), a polar phenylpropanoid that plants bio‐synthesize, universally increases work functions (WFs) of practical electrodes and organic films. Either vacuum‐depositing or spin‐casting CfA films on the electrode materials form a dipole layer with the negative charges on the carboxyl group exposed to the outermost surface. The preferential adsorption of the catechol moiety of CfA onto substrate surfaces drives the molecular orientation, leading to the WF increase up to 0.7 eV. As a consequence, the single‐layer devices with the CfA interlayer facilitate the hole injection in forward bias by a factor of 101–102, which validates the usability of the natural molecule for organic electronics.

Keywords

• caffeic acid
• electrodes
• phenylpropanoids
• sustainable electronics
• work function