Characterization and application of self-assembled monolayers for interfacial modification of organic electronic devices

• Grant number: 20/13917-3
• Support Opportunities: Scholarships in Brazil - Master
• Start date: June 01, 2021
• End date: February 28, 2023
• Field of knowledge: Physical Sciences and Mathematics - Physics - Condensed Matter Physics
• Principal Investigator: Paulo Barbeitas Miranda
• Grantee: Claudia Santana Gonçalves Ferreira
• Host Institution: Instituto de Física de São Carlos (IFSC). Universidade de São Paulo (USP). São Carlos , SP, Brazil
• Associated research grant: 14/50869-6 - INCT 2014: on Organic Electronics, AP.TEM

Abstract

This proposal addresses the study of interfaces in electronic devices based on conjugated polymers (CPs). We will use Sum-Frequency Generation (SFG) vibrational spectroscopy to investigate dielectric/semiconductor interfaces in organic field-effect transistors (OFETs), and semiconductor/metal interfaces in organic photovoltaic cells (OPVs). In OFETs, the SiO2 dielectric will be modified with self-assembled monolayers (SAMs) of the surfactant DMOAP to evaluate whether the side-chains of the surfactant will be able to induce molecular ordering of the C10 and C16 side-chains of the organic semiconductor poly(3-alkyl)thiophene by Van der Waals chain-chain interaction. Analyzing the C-H vibrations of the CP's side-chains in the SFG spectra will allow determining the molecular arrangement of the interfacial poly(3-alkyl)thiophene molecules and also evaluating how this arrangement affects the OFET's performance, since the dielectric/semiconductor interface is the molecular region directly involved in its operation. SFG spectroscopy will also be used to probe how polyelectrolyte chains, such as polyethylenimine (PEI) and poly[(9,9-bis{3'-[N,N-dimethyl]-N-ethylammonium]propyl}-2,7-fluorene)-alt-1,4-phenylene]dibromide (PFN-Br), can be organized to form dipolar layers favorable to the injection of charges at the OPVs' semiconductor/metal interface. Therefore, this study could have important implications to the understanding of how the molecular arrangement of interfacial components can be manipulated and used to improve the performance of organic electronic devices. (AU)