Probing Device Degradation and Electric Fields in Polymeric Field-Effect Transistors by SFG Vibrational Spectroscopy

Author(s)

Motti, Silvia G. ^{[1, 2]} ; Cardoso, Lilian S. ^[1] ; Gomes, Douglas J. C. ^[1] ; Faria, Roberto M. ^[1] ; Miranda, Paulo B. ^[1]

Affiliation

^[1] Univ Sao Paulo, Sao Carlos Phys Inst, CP 369, BR-13560970 Sao Carlos, SP - Brazil

^[2] Ist Italiano Tecnol, Ctr Nano Cience & Technol Polimi, Via Pascoli 70-3, I-20133 Milan - Italy

• Document type: Journal article
• Source: Journal of Physical Chemistry C; v. 122, n. 19, p. 10450-10458, MAY 17 2018.
• Web of Science Citations: 1

Abstract

There is great interest on the study of the semiconductor/dielectric interface of organic field-effect transistors (OFETs), where a conducting channel is formed. Here, we use the interface selectivity, chemical sensitivity, and field-induced enhancement of sum-frequency generation (SFG) vibrational spectroscopy to probe interfacial molecular ordering and degradation processes in poly-3-hexylthiophene (P3HT) OFETs and also the electric field within their dielectric layer (poly(methyl methacrylate), PMMA). P3HT active layers fabricated by the Langmuir-Schaefer method are more orientationally ordered than spin-coated films. Upon electrical degradation of the device in ambient conditions, no noticeable changes were detected in the SFG spectra of the semiconductor/dielectric interface because the sensitivity of our experiment was not enough to detect degraded polymer chains due to loss of SFG electronic resonance enhancement. Perhaps for the same reason, we were also not able to detect any significant changes in the SFG spectra of the P3HT/dielectric interface upon charge accumulation induced by the gate bias. However, we found that upon polarizing the device, PMMA vibrational bands appeared due to field-induced reorientation of its polar groups. Therefore, SFG spectroscopy can be used to probe the electric field within the organic dielectric, including its sign, bringing the possibility of a complete device characterization by nonlinear spectroscopy/microscopy, mapping out the electric field both within the semiconductor and dielectric layers of the OFETs. (AU)

• FAPESP's process: 14/50869-6 - INCT 2014: on Organic Electronics
• Grantee: Roberto Mendonça Faria
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 13/07328-1 - Investigation of interfaces in polymeric light-emitting diodes (PLEDs) by SFG spectroscopy
• Grantee: Douglas José Correia Gomes
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 15/24908-7 - STUDIES OF OXYGEN ATMOSPHERE EFFECTS ON ELECTRONIC TRANSPORT IN ORGANIC PHOTOVOLTAIC DEVICES
• Grantee: Roberto Mendonça Faria
• Support Opportunities: Regular Research Grants
• FAPESP's process: 14/01595-0 - Investigating interfaces in polymeric optoelectronic devices by SFG spectroscopy
• Grantee: Roberto Mendonça Faria
• Support Opportunities: Regular Research Grants