The PhD candidates will acquire knowledge and skills leading them to understand and be able to innovate materials, structure and technology of solar cells. The whole panorama of technologies will be studied,  from the established silicon based technology, up to new concepts based on hybrid and organic materials, quantum dots solar cells, multijunction and concentrator devices. Always taking into account the environmental impact and the life cycle.

  Basic knowledge will be acquired in the common courses that will be given to the doctoral students. Such knowledge will include the fundamental mechanisms of the light-matter interaction, the intrinsic thermodynamic limits in the photovoltaic conversion process and the structure of photovoltaic conversion devices. The goal will be to allow students to handle the figures of merit of solar cells and modules, and to understand how they depend on the topological and technological choices available to the designer. The dependencies of characteristic parameters on operating and environmental conditions, such as temperature and irradiance, will be studied, along with  interactions occurring when several solar cells are connected to each other to form solar modules and complex systems. Parasitic parameters and physical-chemical mechanisms leading to the onset of unexpected and unwanted phenomena, such as overheating or degradation of performance induced by some operating conditions, will be studied as well.

The availability of state-of-the-art facilities and laboratories at the locations involved in the PhD program will allow candidates with solid knowledge of the technological processes used in the fabrication of solar cells. In particular, thin film deposition techniques relying on Chemical and Physical Vapor Deposition, wet chemistry based approaches and the deposition of functional coatings by means of physical / chemical techniques will be studied. A special focus will be given to the relationship between technological processes and electrical performance of photovoltaic devices, with the aim of developing in PhD candidates critical skills aimed at overcoming bottlenecks towards more performing and sustainable future devices.

 The knowledge of basic physics, chemistry and technologies will be completed by giving to PhD candidates the ability to analytically model all phenomena involved in the photovoltaic conversion and by the knowledge of the most advanced numerical analysis tools that allow to recreate in a virtual environment the structure and optoelectronic properties of photovoltaic devices.

At the same time, students will acquire all needed knowledge to characterize, by means of advanced measurement techniques, the figure of merit of solar cells, the optoelectronics properties of absorber layers and individual technological processes. This goal will be pursued by providing proper training on characterization instruments and techniques available in the laboratories involved in the program.

At a more advanced level, it is expected that candidates, depending on their aptitudes, concentrate their studies on salient aspects of specific technologies, chosen among the most promising in the current panorama. For example, PhD candidates will be allowed to deepen technology and/or modeling and characterization of heterojunction solar cells, thin film solar cells  (CdTe, CIGS, CZTS, Sb2Se3, SnS), multijunction solar cells and solar cells based on emerging technologies, such as those based on Perovskite or others.

Last but not least, in all courses, emphasis will be placed on the recycling process at the end of life of solar modules and materials. How the properties of the materials affect the expected lifetime of solar cells, thus determining the Energy Return on Energy Investment (EROEI), will be also studied.

The interdisciplinary nature of the PhD  program will be guaranteed by the provision that candidates will spend part of their time  in different laboratories of the national network and they will attend courses held by both academic and industrial experts with different backgrounds.

Photovoltaic power plant design requires specific solutions depending on the application and on the integration to perform into new or existing contexts. The PhD candidate will study the aspects related to design of large plants, from those ones concerning the modules and their installation, grounding, electrical interconnection and architecture, up to the electronics aspects and the whole balance of system. System level aspects will be studied, in relation to the global performance and efficiency as well as to the lifetime, operation and maintenance. Electrical architectural aspects will be analyzed in order to ensure the best performance, both in terms of power, in specific operating conditions, as well as in terms of energy. System level design for plants including other renewable energy sources, e.g. exploiting wind energy, and storage devices based on different technologies, as well as power-to-gas systems will be the subject of investigation from the students.

Design issues that are specific for innovative photovoltaic applications will also be studied. In this class fall, for instance, photovoltaic building integration, agrivoltaics, floating installations and mobility applications.

Cells technologies ensuring the best adaptation to buildings and electronics aimed at improving the electrical power production in the mismatched conditions that are typical of photovoltaic technology integration in such a context will be the subject of in-depth analyses.

The improved land exploitation by integrating photovoltaic generators with existing or new crops and farms represents an opportunity for reducing the agricultural carbon footprint and improving biodiversity. Such an application gives rise to significant issues requiring a multidisciplinary background, e.g. for balancing the effects of the electrical energy production with the specific crops productivity, as well as specific design competences and photovoltaic technologies.

PhD students’ interest will also be focused on the photovoltaic integration into the landscape by exploiting natural or artificial lakes. These installations avoid to reduce the land availability for other purposes, but require to face technical issues concerning operation and maintenance, reliability and lifetime that will be the subjects of didactical and research efforts. 

The photovoltaic integration into vehicles, ships and, more in general, in the mobility sector, gives rise to solve specific problems. The PhD candidate will afford issues related to the integration into the hybrid or plugin energy system of the vehicle, at the same time by complying with aspects related to aerodynamics, aesthetics, and overall efficiency. Technological problems related to the photovoltaic productivity and modules lifetime in harsh conditions, which characterize many mobility applications and requiring transversal competences in materials engineering, physics and chemistry at least, will also be afforded.   

The PhD candidate will afford studies that are related to all the approaches to the monitoring and diagnosis of photovoltaic systems, with relation to all their parts, from the modules to the supporting structures, to wirings and connection components, up to power electronics and electrical energy storage systems.

The methodologies to use will be inevitably based on a number of competences, which will be given to all the student through the common part of the education plan. Indeed, interdisciplinary knowledge will be needed to have a holistic view of the approaches used in actual and future applications. Image based diagnostic, in the infrared and visible ranges, will need a glance to algorithms for image processing and to issues related to images acquisition through drones. A solid background on Artificial Intelligence (AI) is build up in order to apply powerful data driven approaches to images as well as to electrical, atmospheric, operational data acquired on the modules, on electronics, on switching converters, on the power plant more in general.

Studies on model-based approaches will also be covered, these ones needing a transversal and multi-disciplinary basis related to multi-physics approaches that include electrical and thermal aspects. The competences needed will be provided in the common part of the education plan and they will be related to all the parts of the photovoltaic plant, including the modules and the balance of system.

Approaches based on the analysis of the electrical quantities measured on the photovoltaic plant will be studied, both in the time and in the frequency domain. Model-based and data-driven methods will be exploited also for studying innovative methodologies exploiting digital twins.

Operation-and-Maintenance (O&M) strategies will be afforded to guarantee the highest possible power production along the system lifetime and to extend its Remaining Useful Life (RUL). Prognostic approaches and mitigation actions will be investigated and their feedback over control strategies to improve the RUL will be a topic of interest for the students.

The off-line and on-line implementations of methods and algorithms will be the subject of an in-depth analysis, with a special emphasis on the features offered by modern embedded systems and architectures, to exploit edge-computing features and cloud facilities.

All photovoltaic generation systems are concerning power electronic converters and their control in order to create suitable electric energy links among the different systems involved in the energy conversion scheme. In fact, photovoltaic plants can be directly or indirectly connected to electric grids, storage systems, local loads, electrolyzes for (green) hydrogen production, electric vehicle charging stations, nitrogen liquefaction, etc. All these applications require voltage/current level adaption and/or an ac/dc conversion that can be performed only by power electronic converters with suitable modulation and control.

The PhD candidate will afford studies and improve knowledge related to the analysis, design, testing and control of the above-mentioned power electronic converters. A particular focus is addressed to circuitry and hardware, from power semiconductor devices to power converters and power processors topologies, modulation strategies and to control algorithms.

The power converters design and control require a certain number of basic skills, which will be given to all the student through the common part of the education plan. An interdisciplinary approach is also necessary to make the PhD candidate to have an overview of the technology. The principles of switching converters applied to electrical energy management, as well as the mathematical modeling of power electronic circuits and photovoltaic generators, play a key role for design of the power processor for photovoltaic applications. A solid background on circuit theory, dynamic systems and control theory is given in order to enable the PhD candidate to follow the project of power converters from the initial design up to optimization and verification tests on prototypes, in the view of industrialization and to arrive to final commercial products.

Studies on thermal modeling of power semiconductor devices and their cooling systems will also be covered, giving a multi-physics and multi-disciplinary overview that correlates electrical and thermal aspects, such as power losses and overtemperatures, key points for reliable and efficient converters.

The PhD candidate will also gain knowledge in the field of control theory and will apply control schemes to photovoltaic systems for electricity generation. Traditional and advanced algorithms for maximum power point tracking, as well as control schemes for grid-following and grid-forming inverters will be topics of interest for the PhD candidate. Particular emphasis will be given to the control issues related to photovoltaic generators in case of partial shading and slow- and fast-changing irradiance, together with temperature transients.

The topics of multilevel inverters, isolation converters, interleaved schemes, and innovative power semiconductors, such as Silicon Carbide (SiC) devices, will complete the PhD candidate knowledge in the field of the electricity power conversion applied to large photovoltaic generation systems.

The intrinsic intermittent behavior of the solar source calls for a number of studies, which are useful in order to optimize the operations of photovoltaic (PV) plants.

On the one hand, the PhD candidate will study the integration of photovoltaic plants with energy storage systems (ESS) based on different technologies such as electrochemical, chemical, mechanical and thermal storage, which are used both for energy shift and peak shaving applications.

PV plants and ESS will be integrated in different environments such as nano and microgrids, energy communities and solar-powered e-vehicle charging stations with or without vehicle-to-everything (V2X) capabilities.

On the other hand, the PhD candidate will also tackle the intermittent behavior of the solar irradiance thanks to the opportunity offered by different forecasting tools. These, in fact, allow the forecasting of the solar irradiance and of the operating temperature, which play a key role in the prediction of the power produced by the PV plant.

The studies described above represent the background for the development of efficient battery management systems (BMS) and energy management systems (EMS), which are used for the optimization of the power and the energy fluxes, from both the economic and the environmental points of view. Another aspect to consider is the development of those ancillary services used to make the pairing of PV plants with ESS a reliable source of flexibility for the power system.

For these purposes, the PhD candidate will need to develop different forecasters for the prediction of the load, of the state of charge and health of the storage systems, of the voltage and the frequency of the grid, of the electricity price and of the carbon intensity.

The key competencies required of the candidates, in order to successfully complete this curriculum are: the design of power systems including PV generators and ESS, artificial intelligence-based techniques for the development of control and forecasting tools, optimization techniques and instruments for the assessment of the sustainability of the different developed systems, such as LCA (Life Cycle Assessment), LCOE (Levelized Cost Of Energy) and EROEI (Energy Return on Energy Invested).  

The PhD candidate will be able to develop studies and improve knowledge related to the large and widespread integration of distributed Photovoltaic generation into the present and future power systems, specifically in low and medium voltage distribution grids.  Analysis of the technical, economic, and regulatory problems posed by the variable solar energy source in the evolving of power systems will be within the expertise developed by the candidate.

The study of large-scale distributed grid-connected photovoltaics requires a certain number of basic skills, such as recognition, modelling (deterministic and probabilistic) and simulation of solar energy source, PV technologies and distribution grids.  Power converters basic and control strategies of active and reactive power required for PV grid connection is also required. Such skills will be given to all the student through the common part of the education plan.

An interdisciplinary approach is also necessary to let the PhD candidate have an overview of the PV grid interaction. The knowledge of power systems studies, such as: load flow, optimal power flow, stability analysis (angle, frequency and voltage stability)  and short circuit analysis, play a key role for the deep qualitative and quantitively understanding of the impact of  role of photovoltaic systems in the future smart distribution grids. 

A solid background on circuit theory, dynamical systems and control theory is given to enable the PhD candidate to define the steady-state and dynamic operating point of the PV systems when they are involved in the provision of ancillary services for the Transmission System Operator (TSO) and/or Distribution System Operator  (DSO) within a general liberalized schemes of selling of such services. The microeconomics background will allow to evaluate the economic opportunities coming from the participation of PV systems in the energy and ancillary services markets.

Studies on power quality in distribution grids with distributed PV generation will also be covered including topics such as: power quality standards and applications, evaluation and analysis of voltage fluctuation and flicker and harmonic analysis.

In most cases the PV systems inject into the grid the net power, as a difference between the generated power and the local load, so the PhD candidate will also gain knowledge in the field of the characteristics of the net load in a distribution grid with distributed PV generation. Specifically, methodologies to optimize the self-consumption and self-sufficiency or cost-effectiveness of grid-connected prosumers by optimizing the sizes and/or operation of photovoltaic (PV) systems with or without electrochemical batteries and with the implementation of flexibilization of local load will be considered.

The topics of techniques for mitigating of the impacts of high-penetration photovoltaics (e.g. energy storage technology; demand response; cluster partition control; community-detection-based optimal network partition, aggregation) and design and implementation of stand-alone multisource microgrids with high-penetration photovoltaic generation, will complete the PhD candidate knowledge in the field of the interaction of extended distributed photovoltaic systems with the power system.