Radiofrequency Schottky Diodes Based on p-Doped Copper(I) Thiocyanate (CuSCN)

Schottky diodes based on inexpensive materials that can be processed using simple manufacturing methods are of particular importance for the next generation of flexible electronics. Although a number of high-frequency n-type diodes and rectifiers have been demonstrated, the progress with p-type diodes is lagging behind, mainly due to the intrinsically low conductivities of existing p-type semiconducting materials that are compatible with low-temperature, flexible, substrate-friendly processes. Herein, we report on CuSCN Schottky diodes, where the semiconductor is processed from solution, featuring coplanar Al-Au nanogap electrodes (<15 nm), patterned via adhesion lithography. The abundant CuSCN material is doped with the molecular p-type dopant fluorofullerene C₆₀F₄₈ to improve the diode's operating characteristics. Rectifier circuits fabricated with the doped CuSCN/C₆₀F₄₈ diodes exhibit a 30-fold increase in the cutoff frequency as compared to pristine CuSCN diodes (from 140 kHz to 4 MHz), while they are able to deliver output voltages of >100 mV for a V_IN = ±5 V at the commercially relevant frequency of 13.56 MHz. The enhanced diode and circuit performance is attributed to the improved charge transport across CuSCN induced by C₆₀F₄₈. The ensuing diode technology can be used in flexible complementary circuits targeting low-energy-budget applications for the emerging internet of things device ecosystem.