Ultrafast pump-probe spectroscopy and microscopy of organic semiconductors

• Grant number: 15/19953-3
• Support Opportunities: Scholarships abroad - Research
• Start date: January 04, 2016
• End date: January 03, 2017
• Field of knowledge: Physical Sciences and Mathematics - Physics - Condensed Matter Physics
• Principal Investigator: Paulo Barbeitas Miranda
• Grantee: Paulo Barbeitas Miranda
• Host Investigator: Guglielmo Lanzani
• Host Institution: Instituto de Física de São Carlos (IFSC). Universidade de São Paulo (USP). São Carlos , SP, Brazil
• Institution abroad: Politecnico di Milano, Italy

Abstract

Optoelectronic devices based on conjugated organic materials are becoming an attractive alternative to their inorganic counterparts due to their low cost and increased versatility, since they combine semiconducting properties with the processability and chemical diversity of polymers and small molecules. Organic solar cells, photodetectors and light-emitting diodes are examples of such devices. However, improvements in their performances and device life-time depend on a deep knowledge about the photophysical and electronic processes that occur in the materials. In this proposal we aim at investigating the dynamics of fundamental optoelectronic processes that are relevant for organic devices, such as energy or charge transfer, with a state-of-the-art apparatus at the Italian host institution (POLIMI) that combines ultrafast (~100 fs) temporal resolution and sub-micron spatial resolution. During the candidate's stay at POLIMI, he will get acquainted with the complex setup, combining the traditional ultrafast Pump-Probe Spectroscopy (PPS) with a Confocal Microscope, and use it to investigate charge and/or energy transfer efficiency and dynamics in organic materials, including conjugated polymers that can be used in light-emitting diodes and solar cells. He will also implement a setup for investigating the ultrafast dynamics of interfacial processes based on PPS with visible pump pulses and probe by second-harmonic generation (SHG). This vis-pump/SHG-probe experiment is intrinsically sensitive to the formation of interfacial electric fields due to photoinduced charge-transfer, and will be initially used probe the formation of an electric double layer at conjugated polymer/electrolyte interfaces, which is relevant to their ongoing studies of photoinduced stimulation of neurons for artificial retina applications. The experience acquired during this stay will be very helpful to our plan of implementing an ultrafast spectroscopy setup at IFSC-USP, which could become a pioneer lab in the research on ultrafast spectroscopy of organic electronic materials in Brazil, and may foster a long-term collaboration between the two groups at IFSC-USP and POLIMI. (AU)