Surface Polarization Drives Photoinduced Charge Separation at the P3HT/Water Interface

Abstract
Hybrid devices employing organic semiconductors interfaced with an aqueous solution represent a new frontier in bioelectronics and energy applications. Understanding of the energetics and photoinduced processes occurring at the organic/water interface is fundamental for further progress. Here, we investigate the interfacial electronic structure of poly-3-hexylthiophene (P3HT) sandwiched between an indium tin oxide (ITO) electrode and a liquid water electrolyte. The aqueous solution is found to polarize the polymer outermost layers, which together with the polymer p-(photo) doping by dissolved oxygen localizes photogenerated electrons at the P3HT/water interface, while holes can be transferred to the ITO electrode. Under illumination, the polymer/water interface is negatively charged, attracting positive ions from the electrolyte solution and perturbing the ion distribution in the aqueous solution. The observed mechanism is of general character and could underlie the behavior of a variety of devices characterized by an organic/water interface, such as prosthetic devices for artificial vision and organic-based systems for photoelectrochemical applications.

Citation
Mosconi, E., Salvatori, P., Saba, M. I., Mattoni, A., Bellani, S., Bruni, F., … De Angelis, F. (2016). Surface Polarization Drives Photoinduced Charge Separation at the P3HT/Water Interface. ACS Energy Letters, 1(2), 454–463. doi:10.1021/acsenergylett.6b00197

Acknowledgements
P.S., E.M., F.D.A., A.M., and M.I.S. acknowledge CompuNet Istituto Italiano di Tecnologia, for funding this research. A.M. and M.I.S. thank MIUR and Regione Autonoma della Sardegna (Project Netergit) and CINECA (ISCRA VIPER, SOAP and THESTA). S.B., G.L., and M.R.A. acknowledge the financial support from the European Community through Projects FP7-PEOPLE-212-ITN 316832 (OLIMPIA) and the FET Collaborative Project 309223 (PHOCS), from the Telethon - Italy foundation (Grants GGP12033 and GGP14022) and from Fondazione Cariplo (Grant ID 2013-0738). J.-L.B. acknowledges generous support from King Abdullah University of Science and Technology and ONR-Global (Grant N62909-15-1-2003). The authors acknowledge Wan Ki Bae for the synthesis of the dual-emitting CdSe/CdS heterostructures.

Publisher
American Chemical Society (ACS)

Journal
ACS ENERGY LETTERS

DOI
10.1021/acsenergylett.6b00197

Additional Links
https://pubs.acs.org/doi/10.1021/acsenergylett.6b00197

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