Polymeric microwave rectifiers enabled by monolayer-thick ionized donors

Solution processing of polymeric semiconductors provides a facile way to fabricate functional diodes. However, energy barriers at metal-semiconductor interfaces often limit their performance. Here, we report rectifying polymer diodes with markedly modified energy-level alignments. The gold electrode surface was treated with a dimeric metal complex, which resulted in a shallow work function of 3.7 eV by forming a monolayer-thick ionized donor layer. When a polymeric semiconductor was coated on the treated electrode, most of the ionized donors remained at the metal-semiconductor interface. The confined ionized donors with the ideal thickness enabled fabrication of a polymer diode with a forward current density of over 100 A cm^-2. Furthermore, a power conversion efficiency of 7.9% was observed for rectification at a microwave frequency of 920 MHz, which is orders of magnitude higher than that reported for organic diodes. Our findings will pave a way to solution-processed high-frequency and high-power devices.