Electrical Characteristics of the Junction between PEDOT:PSS and Thiophene-Functionalized Silicon Microwires
Thiophene moieties have been attached to Si microwires (Si MWs) by a two-step chlorination/alkylation reaction method. X-ray photoelectron spectroscopy indicated that saturation of the surface occurred after 30 min of reaction time. Electrical measurements using a standard probe station indicated that the junction between individual thiophene-functionalized Si MWs and the conducting polymer poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS) became more ohmic as more thiophene was added to the MW surface. Under a light-limited current of 20 nA, representative of operation of Si MWs under 1 Sun illumination conditions, the iR loss of thiophene-n-Si MW/PEDOT-PSS contacts was 20 mV, representing an order of magnitude reduction compared with PEDOT-PSS junctions formed with methyl terminated n-Si MWs. Such iR losses are much less than typical catalytic overpotentials for fuel formation, and hence the thiophene-functionalized Si MW contacts will not limit the performance of a Si MW array-based solar fuels device under 1 Sun illumination.
© 2015 American Chemical Society. Received: August 19, 2015; Accepted: November 17, 2015; Published: November 17, 2015. Financial support from the Natural Sciences and Engineering Research Council (NSERC) of Canada, the Canada Foundation for Innovation (CFI), the Manitoba Research and Innovation Fund, and the University of Manitoba is gratefully acknowledged. The work reported made use of surface characterization infrastructure in the Manitoba Institute for Materials. This work was supported by the NSF grant No. CHE-1214152 and made use of the Molecular Materials Research Center of the Beckman Institute at Caltech and the Kavli Nanoscience Institute at Caltech. This research was undertaken, in part, thanks to funding from the Canada Research Chairs Program. The authors declare no competing financial interest.
Supplemental Material - am5b07725_si_001.pdf