ECE 443 - LEDs and Solar Cells
Industrial finite element modelling Crosslight software is used during the hands-on computer labs for the design and simulation of quantum structures, light emitting diodes, and solar cells. For each lab set, there will be one in-class quiz to assess the student learning.
The class involves a final project. This will be an open-ended research project of student's choice. The report is written following the National Science Foundation-style. Students are encouraged to work in pairs/teams, and to think of topics as the course progresses. However, each student will have one independent project submission.
NanoFab cleanroom located in the ECE Building is used for the cleanroom activities related to the characterization of light emitting diodes and solar cells. There will be a formal report for each lab set. The select topics of NANOFAB labs are: 1. Safety Training; 2. SEM Training & SEM Inspection of LEDs and Solar Cells; 3. Identification of leakage paths and loss mechanisms in LEDs; 4. Effects of temperature on LED characteristics; 5. Identification of leakage paths and loss mechanisms in a solar cells; 6. Effects of temperature on Solar Cell characteristics and Series/Parallel-connected Solar Cells.
No single textbook covers all topics. The course will rely on recent news items, journal papers, lecture handouts, lecture notes/slides, and reading sections from several books including “Light Emitting Diodes” by E. Fred Schubert (Cambridge, 2003) and “The Physics of Solar Cells” by J. Nelson (Imperial College Press, 2003).
This course explores the energy conversion devices from fundamentals to system-level issues. The course starts with a review of the electronic structure of atoms and semiconductors, quantum physics, and compound semiconductors. Then semiconductor heterostructures and low dimensional quantum structures, forming the basis of modern devices such as light emitting diodes and solar cells are introduced. Topics covered include energy transfer between photons and electron-hole pairs, light emission and capture, emission and absorption engineering via device simulation/design, radiative and non-radiative processes in devices, electrical and optical characteristics, carrier diffusion and mobility, and light extraction and trapping for high efficiency devices. Computer labs and cleanroom labs reinforce modern device design and analysis such as light emitting diodes and solar cells.
A. By the time of the Midterm Exam (after fifteen classroom lectures, three sets of experimental laboratories, and two sets of computer laboratories), the students should be able to do the following:
1. List common applications of LEDs and Solar Cells (7)
3. Understand electrical, structural, and optical effects of impurities on semiconductors. (1)
4. Calculate lattice constants and bandgap energies of III-V ternary and quaternary compound semiconductors using Vegard's law. (1)
6. Calculate energy band discontinuities at the heterojunctions by back-of-the-envelope calculation, freeware BandEng simulator, and industrial Crosslight Software and identify limitations in each approach. (1)
7. Find the allowed energy levels and the density of states in quantum well structures by back-of-the-envelope calculation and Crosslight Software. (1)
8. Establish the physical understanding of light reflection, light absorption, and spontaneous emission rates by using Einstein relations. (1)
9. Explain the operating principles of LEDs and explain threshold voltage, quantum efficiency, power efficiency, luminous efficiency, color rendering, and other figures of merit and their temperature behavior. (1)
10. Understand the equivalent circuit model of a LED. (1)
11. Measure and assess light extraction, internal, and external efficiencies of LEDs and their temperature-dependent behavior. (1)
12. Explain the fundamentals of solid-state lighting (SSL) and identify SSL’s current challenges. (4)
15. Experimentally measure I-V and spectrum of a LED and extract data concerning the internal loss, external quantum efficiency, internal quantum efficiency, output power, and threshold current. (1) (6) (7)
B. By the time of the Final Exam (after twenty classroom lectures, six sets of experimental laboratories, and five sets of computer laboratories), the student should be able to do all of the items listed under A plus the following:
17.Understand the differences between photoconductivity and photoelectricity. (1)
18. Understand the differences between a battery and a solar cell. (1)
19. Explain the operating principles of solar cells and explain fill factor, short circuit current, open circuit voltage, internal quantum efficiency, external quantum efficiency, and other figures of merit and their temperature behavior. (1)
20. Understand the equivalent circuit model of a solar cell. (1)
22. Develop the ability to design single and multi-junction solar cells by optimizing semiconductor material parameters and heterojunction engineering using freeware wxAMPs simulator and Crosslight Software and identify limitations in each approach. (1) (2)
23. Explain the fundamentals of photovoltaics (PV) and identify PV’s current challenges. (4)
24. Identify present and future areas of applications for PVs. (4)
25. Simulate heterojunction solar cells by optimizing semiconductor material parameters and establish the physical understanding of various design parameters in solar cells. (1)
26. Experimentally measure I-V and IQE of a solar cell and extract data concerning the internal loss, external quantum efficiency, internal quantum efficiency, output power, short circuit current, and open circuit voltage. (1) (6) (7)
28. Address a need in the society through a new design of a LED or a Solar Cell using Crosslight Software, analyze and write a professional report on the design choices and outcomes, and present the final design and findings to the class. (3) (4) (6) (7)