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Published July 18, 2013 | Supplemental Material
Journal Article Open

Electrical Junction Behavior of Poly(3,4-ethylenedioxythiophene) (PEDOT) Contacts to H‑Terminated and CH_3‑Terminated p‑, n‑, and n^+‑Si(111) Surfaces

Abstract

The electronic and photovoltaic properties of junctions between the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) and Si(111) surfaces have been investigated for a range of doping types, doping levels, and surface functionalization of the Si. PEDOT–poly(styrenesulfonate) (PSS) formed ohmic, low resistance contacts to H-terminated and CH_3-terminated p-type Si(111) surfaces. In contrast, PEDOT formed high barrier height (0.8–1.0 V) contacts to n-Si(111) surfaces, with CH_3-terminated n-Si(111)/PEDOT contacts showing slightly higher barrier heights (1.01 eV) than H-terminated n-Si(111)/PEDOT contacts (0.89 V). PEDOT contacts to CH_3-terminated and H-terminated n-Si(111) surfaces both produced photovoltages under illumination in accord with the Shockley diode limit based on bulk/recombination diffusion in the semiconductor. Such devices produced solar energy-conversion efficiencies of 5.7% under 100 mW cm^(–2) of simulated air mass 1.5 illumination. The electrical properties of PEDOT contacts to CH_3-terminated Si surfaces were significantly more stable in an air ambient than the electrical properties of PEDOT contacts to H-terminated Si surfaces. PEDOT films produced a low resistance, tunnel-barrier type of ohmic contact to n^+-Si(111) surfaces. Hence, through various combinations of doping type, doping level, and surface functionalization, the PEDOT/Si contact system offers a wide range of opportunities for integration into monolithic photovoltaic and/or artificial photosynthetic systems.

Additional Information

© 2013 American Chemical Society. Received: February 20, 2013; Revised: May 6, 2013; Published: May 8, 2013. We acknowledge the National Science Foundation Grant CHE-1214152 for financial support. We acknowledge critical support and infrastructure provided for this work by the Kavli Nanoscience Institute at Caltech. M.G.W. acknowledges support from a NSF American Competitiveness in Chemistry postdoctoral fellowship (CHE-0937048). Additional information regarding the preparation and measurements of the PEDOT:PSS films and J–V data of aged electrodes. This material is available free of charge via the Internet at http://pubs.acs.org.

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August 19, 2023
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