Photovoltaics

Course manual 2016/2017

Course content

Photovoltaic conversion brings the promise of sustainable energy generation capable of meeting the ever growing demand. This explains the current interest and is best illustrated by the massive deployment of solar panels in solar farms and integrated systems in countries worldwide. This lecture course introduces the most important concepts from solid-state physics and (nano)technology which form scientific foundations of photovoltaics, giving a starting point for understanding of its principles, prospects, as well as limitations and bottlenecks. The lectures are given by work-group leaders working at UvA, AMOLF and also ECN, and next to the basics of operation and application will provide also a comprehensive overview of current activities at the forefront of the research in the field of modern (nano)photovoltaics.

After a short resume on light matter interactions and optical resonances, the following topics will be addressed in some detail:

• Photovoltaic cells, modules and systems
• Light management for photovoltaics
• Nanomaterials for photovoltaics
• Nanohybrid solar cells
• Solar shapers and concentrators

Besides lectures, trips to laboratories of AMOLF and ECN (Petten) will be organized to illustrate the photovoltaic research in practice. For those interested, the course can provide an ideal gateway to a research project for the last year of the MSc track.

Study materials

Other

• Lecture notes.
• Original research articles.

Objectives

Having successfully completed this course you will:

• be able to describe how the photovoltaic cell works and understand the physic processes determining its spectral response, internal and external efficiency and limitations.
• be able to show explain the limiting factors and bottleneck of photovoltaics
• be aware of (some) of the prominent research avenues towards highly efficient (nano)photovoltaics of next generation. Within the general introduction of to the physics and materials science behind the modern photovoltaics, some of the specific objectives of the course include:

Understanding how solar cells work:

• Light absorption in semiconductors – Fermi’s golden rule, LDOS, band structure 
• Charge separation – excitons vs. free carriers, drift vs. diffusion
• Carrier collection – selective contacting schemes (doping, heterojunction, tunnel/MIS)
• Resistive losses – I 2R power dissipation, consequences for solar cell design
• Optical losses – parasitic absorption, reflection, emission
• Excitons – properties, spectral signatures, separation schemes
• Recombination – SRH, surface states, grain boundaries, band-to-band (radiative)
• Thermalization – electron-phonon coupling, energy loss/heat generation
• Timescales – thermalization, PL, exciton splitting, non-rad recombination, trapping
• Meaning/origin of Voc – quasi Fermi level splitting, radiative limit, non-idealities
• Origin Jsc – material absorption coefficient, overlap with solar spectrum
• Meaning/origin of FF – thermodynamic formulation, non-idealities
• Temperature dependence – effect on Voc, Jsc, FF, efficiency

PV systems: 

• From cell to module – interconnection schemes/processes and encapsulation
• Inverters and trackers
• Losses from cell to module and system – cell efficiency variations (temperature, intensity, spectrum), shading, IR loss, dc/ac conversion

PV materials:

• Silicon (sc, mc, a-Si), CIGS, CdTe, GaAs, InP, InGaP, CuZnSnS, DSSC, OPV, QDSCs, perovskite – Why do we (not) work on them?
• Molecular semiconductors - The importance of the dielectric constant, exciton delocalization, morphology, excess energy, spin for recombination, singlet fission
• Perovskite semiconductors – material tenability, excitons vs. charges, photophysics

PV limits:

• SQ detailed balance limit – integrating solar spectrum, VOC with PV as blackbody
• Auger recombination  Multijunction PV – epitaxial growth, current matching, tunnel junctions
• Concentrator PV – voltage/efficiency vs. conc., concentration schemes, cooling needs
• PV limits under upconversion and downconversion: MEG, singlet fission, photon upconversion

Basics of PV device structures/fabrication methods:

• Crystalline silicon – doping schemes (diffusion, implantation) and profiles, emitter resistivity, relating doping level to resistivity, n vs. p base, difference between standard, MWT, IBC, HIT cells, contact formation, passivation schemes, AR coatings
• Thin-film (CdTe, CIGS, OPV, perovskite, QDs) – layer geometry, factors affecting conversion efficiency, grain boundaries, stoichiometry, defects (vacancies, interstitials, anti-site), heterojunctions, TCOs, contacts

Basics of PV characterization measurements:

• J-V curves – how to collect them, what changes them (diode equation, non-idealities)
• Solar simulators – calibration via reference diodes, spectral mismatch correction
• EQE – how to measure, what does it mean, why there is spectral effect
• Comparing Jsc from EQE integration with Jsc from J-V curve
• Absorption and reflection measurements and simulations (optical modelling)– how they are done (integrating sphere)  IQE measurements – what they mean, what the spectral dependence tells you
• Carrier lifetime measurements – methods, typical values
• Carrier diffusion length – how it is measured/calculated, relation to lifetime
• PL – how it is collected, what it tells you, efficiency, lifetime
• Electroluminescence – how it is collected, what it tells you, reciprocity PV/LED
• Surface recombination velocity – evaluation, measurement, reduction
• Band gap determination – absorption (Tauc plot) vs. PL vs. EQE cut-off
• Material composition/crystallinity – XRD, SAED, TEM, EDS, SIMS, AES, XPS, XRF
• Time-resolved techniques – transient absorption, photovoltage and photocurrent decay

Nanoscale PV effects:

• Quantum confinement – exciton Bohr radius, scaling of band gap, relaxing k-space
• Multiple exciton generation – explanation improved yield in nanoscale systems
• Quantum cutting/pasting – comparison with Auger effects, phonon bottleneck
• Optical resonances – large cross section/concentration, size/shape effect, plasmon/Mie modes
• Directionality – directional scattering/emission, effect on Voc and concentration
• Nanomaterials as TCO alternative – metal nanowires, CNT, graphene
• Periodic nanostructures – gratings, coupling to waveguide modes
• Light trapping – periodic vs. disordered, exceeding 4n2 in wave regime
• Nanoscale AR coatings – graded index, impedance matching, resonant in-coupling

Teaching methods

• Lecture
• Fieldwork/excursion
• Presentation/symposium
• homework assignments

Lectures and moderated discussions by teachers, presentations by students, homework assignments.

Learning activities

Attendance

The programme does not have requirements concerning attendance (OER-B).

Additional requirements for this course:

Assessment

The course will be assessed on the basis of homework assignments and presentations: participation in both is obligatory to be considered for passing the course.  There will be no exam at the end of the course.

Homework assignments will be given once a week – a single assignment per every lecturer. They will have to be delivered individually within a week. Teaching assistants (TA, one TA per lecturer/assignment) will be available for on-line consultations all the time and students are encouraged to make use of that. After delivery, your homework will be checked and graded by TA’s. The individual grades will appear on Blackboard site of the course; feedback will be provided by TA’s on-line and upon request.

Materials for students’ presentations will be assigned during the first lecture and the relevant material will be placed on the Blackboard site. Every student will be asked to prepare a presentation during the course (one per student). All the students are expected to familiarize him/her-self with the article to be presented during a particular lecture, prepare at least one question, and take active part in the discussion. Presentations and the follow-up discussion (answers as well as questions) will be graded. The feedback for the presenters will be directly given.

The final grade will be an average of the graded assignments (5) and a presentation (1) – equally weighted, so:

(5×grade assignment + 1×grade presentation)/6 = final grade.

In order successfully complete the course all the assignments need to be handed in and a presentation has to be given.

Assignments

Onderstaande opdrachten komen aan bod in deze cursus:

•    Naam opdracht 1 : beschrijving 2
•    Naam opdracht 2 : beschrijving 1
•    ....

Fraud and plagiarism

Dit vak hanteert de algemene ‘Fraude- en plagiaatregeling’ van de UvA. Onder plagiaat of fraude wordt verstaan het overschrijven van het werk van een medestudent dan wel het kopiëren van wetenschappelijke bronnen (uit bijvoorbeeld boeken en tijdschriften en van het Internet) zonder daarbij de bron te vermelden. Uiteraard is plagiaat verboden. Hier wordt nauwkeurig op gecontroleerd en streng tegen opgetreden. Bij verdenking van plagiaat wordt de examencommissie van de opleiding ingeschakeld. Wanneer de examencommissie overtuigd is dat er plagiaat gepleegd is dan kan dit maximaal leiden tot een uitsluiting van al het onderwijs van de opleiding voor een heel kalenderjaar. Zie voor meer informatie over het fraude- en plagiaatreglement van de Universiteit van Amsterdam.www.uva.nl/plagiaat

Course structure

Timetable