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Lecture

Weak Bond Model: Defects in Electronic Materials

In course

MICRO-566: Large-area electronics: devices and materials

Introduction to the physical concepts involved in the description of optical and electronic transport properties of thin-film semiconductor materials found in many large-area applications (solar cells, displays, imagers, etc) and introduction to the physic ...

Description

This lecture delves into the Weak Bond Model, focusing on equilibrium defect densities, band tail models, defect creation, and Fermi-Dirac type integrals. It explores the positions of defect distributions, defect formation energies, and defect pools in electronic materials.

Instructors (2)

Christophe Ballif

Christophe Ballif is director of the Phototovoltaics and Thin Film Electronics Laboratoryb) (PV-Lab at the institute of microengineering (IMT) in Neuchâtel (part of the EPFL since 2009). The lab focus is on the science and technology of high efficiency heterojunction crystalline cells,so-called passivating contacts for solar cells, multi-junction solar cells include novel generation Perovskite on innovative optical high speed detector and on various macroelectronics application. It also deals with energy management with a focus on integration of solar electricity into the energy system. The PV-Lab has strongly contributed to technology transfer and industrialization of novel devices and full technology with numerous companies. Christophe Ballif graduated as a physicist from the EPFL in 1994, where he also obtained in 1998 his Phd degree working on novel PV materials. He accomplished his postdoctoral research at NREL (Golden, US) on compound semiconductor solar cells (CIGS and CdTe). He worked then at the Fraunhofer ISE (Ge) on crystalline silicon photovoltaics (monocrystalline and multi-crystalline) until 2003 and then at the EMPA in Thun (CH) before becoming full professor at the University of Neuchâtel IMT in 2004, taking over the chair of Prof. A. Shah. Since 2013, C.Ballif is also the director of the new CSEM PV-Center, also located in Neuchâtel. The CSEM PV-Center is focussing more on industrialisation and technology transfer in the field of solar energy, including solar electricity management and storage. At the core of the CSEM PV-center activities lies several "pilot lines" for various kinds of solar cells manufacturing, with a focus coating technologies, wet chemistry processes for crystalline silicon, metalisation techniques for solar cells, and a platform for developing "ideal packaging solutions and polymers" for PV modules. In addition, joined facitilites between CSEM and EPFL of over 800 m2 are available for modules manufacturing, measuring and accelerated aging. CSEM PV-center has also full team dedicated to storage and energy systems and operates a joined center with BFH in Biel for research on electrochemical storage. He (co-) authored over 500 journal and technical papers, as well as several patents. He is an elected member of the SATW, member of the scientific council of the Swiss AEE, and member of the board of the EPFL Energy center. In 2016, he recieved the Becquerel prize for his contributions to the field of high efficiency photovoltaics.

Franz-Josef Haug

I studied Physics between 1990 and 1996 at the Universities of Ulm (Germany) and Waikato (New Zealand). While specializing mostly on Theoretical Physics and Quantum Theory during my studies, I turned towards Experimental Physics for a graduate work on gas-phase epitaxy of silicon. After that, I pursued a PhD program at ETH Zürich (Switzerland), studying Cu(In,Ga)Se2 solar cells. As PostDoc, I went to EMPA (Switzerland) to work on plasma processes for hard coatings of TiN and to the Jülich Research Centre in Germany to study light scattering ZnO front contacts for solar cells. In 2005 I joined the Institute of Microengineering (IMT) at the University of Neuchatel to lead a research group on thin film silicon solar cells within the PV-Lab. In 2009 the IMT was integrated into EPFL. My main research interests are optics, charge transport in semiconductors and renewable energy in general. My current work is devoted to passivating contacts for crystalline silicon solar cells, using thin silicon films as contact layers. In 2015 I was appointed Maitre d'Enseignement et Recherche (Senior Lecturer and Scientist) and member of the Faculty of STI. From 2013 to 2015 I was member of the EFPL Teachers Council (CCE) and from 2016 and 2018 I was elected into the Council of the Engineering School (CF-STI). In 2020 I was elected to become a member of CF-STI. My main objective for the legislature is to represent the role of EPFL's intermediate staff and to raise the awareness for concerns of the satellite campuses.

Official source

Ontological neighbourhood

Physics

Condensed matter physics: Solid-state physics

Related concepts (32)

Chemical bond

A chemical bond is a lasting attraction between atoms or ions that enables the formation of molecules, crystals, and other structures. The bond may result from the electrostatic force between oppositely charged ions as in ionic bonds, or through the sharing of electrons as in covalent bonds. The strength of chemical bonds varies considerably; there are "strong bonds" or "primary bonds" such as covalent, ionic and metallic bonds, and "weak bonds" or "secondary bonds" such as dipole–dipole interactions, the London dispersion force, and hydrogen bonding.

Doping (semiconductor)

In semiconductor production, doping is the intentional introduction of impurities into an intrinsic semiconductor for the purpose of modulating its electrical, optical and structural properties. The doped material is referred to as an extrinsic semiconductor. Small numbers of dopant atoms can change the ability of a semiconductor to conduct electricity. When on the order of one dopant atom is added per 100 million atoms, the doping is said to be low or light.

Materials science

Materials science is an interdisciplinary field of researching and discovering materials. Materials engineering is an engineering field of finding uses for materials in other fields and industries. The intellectual origins of materials science stem from the Age of Enlightenment, when researchers began to use analytical thinking from chemistry, physics, and engineering to understand ancient, phenomenological observations in metallurgy and mineralogy. Materials science still incorporates elements of physics, chemistry, and engineering.

Semiconductor

A semiconductor is a material which has an electrical conductivity value falling between that of a conductor, such as copper, and an insulator, such as glass. Its resistivity falls as its temperature rises; metals behave in the opposite way. Its conducting properties may be altered in useful ways by introducing impurities ("doping") into the crystal structure. When two differently doped regions exist in the same crystal, a semiconductor junction is created.

Double bond

In chemistry, a double bond is a covalent bond between two atoms involving four bonding electrons as opposed to two in a single bond. Double bonds occur most commonly between two carbon atoms, for example in alkenes. Many double bonds exist between two different elements: for example, in a carbonyl group between a carbon atom and an oxygen atom. Other common double bonds are found in azo compounds (N=N), imines (C=N), and sulfoxides (S=O).

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