Measurement of the Electrical Resistance of n-Type Si Microwire/p-Type Conducting Polymer Junctions for Use in Artificial Photosynthesis

Abstract

The junction between n-type silicon microwires and p-type conducting polymer PEDOT:PSS (poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate)) was investigated using a soft contact method. Dopant levels within the microwires were varied during growth to give a highly-doped region for improved contact and a low-doped region for light absorption. The low-doped region of the microwires had a dopant density of 5 X 10(17) cm(-3) while the highly-doped region had an increased dopant density of 5 X 10(18) cm(-3) over similar to 20 mu m. Uniform, highly-doped microwires, with a dopant density of 4 X 10(19) cm(3), were used as a comparison. Regions of highly-doped n-type Si microwires (N-D = 5 X 10(18) cm(-3) and 4 X 10(19) cm(-3)) contacted by PEDOT:PSS showed a significantly lower junction resistance compared to the low-doped (3 X 10(17) cm(-3)) regions of the microwire. Junctions incorporating the metal catalyst used during growth were also investigated. Microwires with copper at the interface had similar currentvoltage characteristics to those observed for the highly-doped microwire/conducting polymer junction; however, junctions that incorporated gold exhibited significantly lower resistances, decreasing the iR contribution of the junction by an order of magnitude with respect to the total voltage drop in the entire structure.