LEARNING OUTCOMES

Basic knowledge of chemical and physical properties of conjugated polymers and organic semiconductors. Use of such materials in organic optoelectronics and photonic devices (sensors, transistor, led and photovoltaic cells)

AIMS AND LEARNING OUTCOMES

At the end of the class, students are expected to understand:

Main differences between the electronic structure of organic and inorganic semiconductors. Main qualitative differences of the electronic structure of isolated and interacting chains. The concept of energy gap, bandwidth, carrier mobility and intermolecular interactions. The meaning of conjugation length. The qualitative role of disorder in polymer semiconductors on the carrier mobility. 

The importance of solubility in pocessing. The qualitative effect of side chains on processability, controlling intermolecular interactions and solubility.

Methods to  make conjugated polymers oriented and the qualitative effect on the optical properties

Main synthetic strategies to prepare conjugated polymers. The role of regioregularity. Tuning of the ionization potential, electron affinity and energy gap.

Fundamentals of spectroscopy and photophysics in organic semiconductors. The vibronic structure.

Working principlies of  sensors, transistor, led and photovoltaic cells. Material strategies to improve their performances.

They have to be able to extract simple information on physical and chemical properties from absorption/fluorescence spectra of a conjugated polymer/molecule as described during the class with several examples.

PREREQUISITES

Good knowledge of chemistry and physics of materials.

TEACHING METHODS

Lectures delivered by Power Point presentations available to students on AulaWeb. Simple classroom experiments on light matter interaction.

In case of emergency and only according to specific indications by the University of Genoa, the assessment method for the exam might be changed, including the possibility of an online procedure.

SYLLABUS/CONTENT

Section 1: electronic states & spectroscopy

Extended p-electron systems both in molecules and polymers. Conjugation length: ionization potential, electron affinity and HOMO-LUMO gap in the series ranging from ethylene to polyene. Electronic states for the polyene: introduction to the Hückel method for the isolated chain and for interacting macromolecules. Dimerization and Peierls distorsion: metal and semiconducting polymers. Conducting conjugated polymers: doping and applications. Charge transport in semiconducting and conducting polymers. Spectroscopy of conjugated systems: electronic transitions, Franck-Condon principle and vibronic transitions, fluorescence and lifetime, singlet and triplet excitons, Jablonski diagram and photophysics.

Section 2: Synthesis & material processing

Synthesis of main conjugated polymer families (polyacetylene, polythiophene, poly(p-phenylenevinylene)). Functionalization of chemical and physical properties of conjugated materials (solubility, ionization potential, electron affinity). Supramolecolar structure of conjugated polymers and role of aggregation in the solid state. Orientation techniques of conjugated polymers, optical and electronic properties anisotropy.

Section 3: Optoelectronic Devices

Working principles of devices made of conjugated molecules and polymers: sensors, devices for non-linear optics, OLED, PLED, OFET, photovoltaic cells and light harvesting based devices, wearable electronics. Role of the supramolecular structure on the main electronic properties of materials and of devices.

For studentes in Industrial Chemistry, a shorter program holds (4 cfu instead of 6 cfu). In particular, they are allowed to skip the details of electronic structure calculations and light-matter interaction 

RECOMMENDED READING/BIBLIOGRAPHY

References & Books

• Lessons notes provided by the teacher (D. Comoretto)
• Selected papers published on international scientific journals.
• M. Pope and C. Swemberg “Electronic processes in organic crystals and polymers”, Oxford Sci Publ. New York 1999. (Chapter 1).
• M. Klessinger and J. Michl “Excited states and photochemistry of organic molecules”, VCH, New York 1995. (selected paragraphs)
• J.B. Birks “Photophysics of Aromatic Molecules”, Wiley monographs in chemical physics, 1970. (selected paragraphs)
• M.C. Petty "Molecular Electronics", Wiley 2007. (selected paragraphs)