|SCIENTIFIC DISCIPLINARY SECTOR||FIS/03|
The course describes the physical mechanisms underlying the direct conversion of solar radiation into electrical energy by exploiting the photovoltaic effect. The fundamental thermodynamic limits for efficiency and the constraints on the choice of materials and on the construction parameters of high efficiency devices will therefore be understood. Finally, a laboratory activity aimed at electro-optical and morphological characterization of commercial solar cells is planned.
The course aims to illustrate the potential of the solar resource and the physical mechanisms underlying the conversion of solar radiation into electrical energy. The semiconductor physics elements necessary to describe the functioning of solar cells with particular reference to those based on silicon absorbers will be introduced. Finally, we will provide an overview of the new concepts and materials designed to increase the efficiency of solar cell together and an introduction to the experimental characterisation of Solar cells (morphological, optical, electro-optical).
(i)The course objectives include the acquisition of theoretical knowledge related to: Solar energy resource and the sizing of photovoltaic production potential assessed through the use of reference simulation software (PVGIS) available on Open Access platforms. Optical absorption processes in semiconductors. Physics of solar cells and semiconductors, with particular reference to silicon junction devices. Thermodynamic limits to the efficiency of a photovoltaic converter and new concepts and materials to increase the efficiency of solar cells.
(ii) The student will be able to critically discuss the physical limits to the conversion efficiency of photovoltaic devices, and the effect on the efficiency of physical parameters and constituent materials.
(iii) The student will be able to apply the knowledge acquired to complete the correct sizing of a photovoltaic system, to estimate the potential of solar radiation and photovoltaic production in a specific location, also using open source software simulation tools (PVGIS).
(iv) The educational objectives of the course also include the acquisition of experimental skills relatively to the electro-optical and morphological characterization of commercial solar cells.
The specific training activities and skills (i-iv) are indicated both for the "Materials Scientist: Research Specialist" profile and for the "Materials Scientist: Technology Specialist" profile. Activities (iii) and (iv) are also particularly relevant for the "Materials Scientist: Technology Specialist" profile.
The knowledge of the basic concept of Solid Physics and Quantum Machanics are considered to be acquired with particular reference to the behavior of electrons in metals and semiconductors. A prerequisite is also the knowledge of general and Modern Physics Physics with particular reference to electromagnetism, optics and radiation-matter interaction.
The course comprises about 42 hours of classroom lectures in which the theoretical topics are presented. Approximately 8 hours of laboratory activity are also planned in which the characterization of commercial solar cells is carried out with regard to their optical response, morphology and structure, their electrical response under illuminated conditions.
1. Introduction: renewable energy, global warming, energy policy 2- Solar energy resource: Solar radiation. Spectrum of a black body; Effects terrestrial atmosphere on solar radiation: absorption from atoms and molecules and spectral distribution of solar radiation. Absorption from semiconductors; Optical processes; Concentration of solar radiation; 3- Physics of solar cells: Recalls of semiconductor physics. Absorption of photons and generation of electron-hole pairs; Recombination of electrons and holes (radiative and non-radiative). Recombination at grain boundaries, defects and surfaces; Dissemination of minority carriers; lifetime and diffusion length of minority carriers; 4- Basic structure of a Silicon solar cell: p-n and p-i-n Junction . Separation of electrons and holes; I-V characteristic of a solar cell. Monocrystalline solar cells; Polycrystalline solar cells; Theoretical limits for energy conversion (Schockley-Queisser approach); Efficiency and energy gap; Spectral response; Effect of parasitic resistances; temperature effects;
5- New concepts and materials to increase the efficiency of solar cells: Losses by reflection; Concentrating solar cells. Thin-film solar cells; Amplification of Photon Collection in nanostructured cells; Introduction to other semiconductor materials of photovoltaic interest; Thermodynamic limits to the efficiency of a thermodynamic solar converter; Tandem cells (multi-junction) (outline). Intermediate band cells (outline); Cells with warm carriers (outline); Impact ionization cells (outline). 6- Laboratory activities Electro-optical and morphological characterization of commercial solar cells
• “Handbook of Photovoltaic Science and Engineering” Eds. A.Luque and S. Hegedus, Wiley
• “The Physics of Solar cells” by Jenny Nelson (Imperial College, UK) World Scientific Press
• “Materials Concepts for Solar Cells” by Thomas Dittrich (Imperial College Press) 2nd edition
Office hours: M. C. Giordano: available by appointment from Monday to Friday, Physics Department, Office S810 .
FRANCESCO BUATIER DE MONGEOT (President)
MARIA CATERINA GIORDANO (President Substitute)
CORRADO BORAGNO (Substitute)
Normally the start of lessons is scheduled during the first week of March.
All class schedules are posted on the EasyAcademy portal.
The exam will consist in an oral interview lasting about 45 minutes, on a date that can be agreed with the teacher who must be contacted well in advance.
The oral exam will be held in the presence of two professors belonging to the commission, at least one of which chosen between F. Buatier de Mongeot and M.C. Giordano.
During the exam the student can illustrate one of the topics of the program of his choice (about 1/3 of the test) while the remaining time of the test is dedicated to deepening the remaining parts of the program.
During the oral exam, the actual achievement of the expected learning outcomes will be verified. The level of knowledge acquired on specific points of the program will be verified, the degree of understanding with respect to the role of the physical mechanisms that determine the operation and efficiency of a photovoltaic device, and the critical ability in dealing with specific cases set by the teacher. The quality of the exposure, the correct use of the specialist vocabulary, the ability to reason critically with respect to specific cases posed by the teacher are also assessed.