Physics pedagogy

  • Physics GRE study sheet: Click here for PDF
    • A review-and-memorization sheet I made when preparing for the Physics GRE in college. The file (an older version) is also hosted here.

    The Shockley-Queisser limit for the maximum possible efficiency of a solar cell (black), and the inevitable losses that limit it (other colors). The black height is energy that can be extracted as useful electrical power; the pink height is energy of below-bandgap photons; the green height is energy lost when hot photogenerated electrons and holes relax to the band edges; the blue height is energy lost in the tradeoff between low radiative recombination versus high operating voltage.

  • Shockley-Queisser limit: Click here for my tutorial slideshow, or click here for calculation code (Python) with discussion (if you want to run the code yourself, use this link)
    • In 1961, William Shockley and Hans-Joachim Queisser famously proved that certain types of solar cells cannot be more than ~35% efficient. Here you can learn how that calculation works in detail, and also how and why various types of solar cells are able to exceed the limit. The Python code includes not only calculation of the efficiency itself, but also harder-to-find related calculations: Plots of the ideal “VOC” and “ISC“, and detailed breakdowns of the losses. I used this program to make some graphs that I uploaded to Wikipedia, like the one on the right –>
  • Ultimate solar power efficiency limit: Click here (download source code as IPython notebook)
    • This is a detailed derivation of the “ultimate” solar power efficiency limit, which is higher than the Shockley-Queisser limit because it applies more broadly to essentially any possible solar power system.
  • Introduction to Schottky-Barrier and “MIS-IL” solar cells: PAPER and PRESENTATION
    • This is a type of solar cell commonly used in laboratory studies but not commercially viable today. I wrote this as a term paper in a grad-school course on the physics of solar cells (“NSE 290” at UC Berkeley).
  • Polarons: Click here for PDF
    • This a brief introduction to “polarons”, a concept in solid-state physics. I wrote it for a grad-school course on semiconductor materials (“MSE 223” at UC Berkeley).
  • Fermi-level terminology guide: Click here
    • This is my guide to the confusing and inconsistent way that the terms “fermi level”, “fermi energy”, “electrochemical potential”, “chemical potential”, etc., are used in different fields of physics and chemistry.
  • Phonon pumping: Click here for PDF
    • This is a paper about whether you can make a laser from silicon (or other “indirect-bandgap” materials) by “phonon pumping”–i.e., trying to set up stimulated emission of phonons and photons simultaneously. (A normal laser is just photons.) I thought it was a great idea for a few days, but then discovered that it doesn’t work. (There are too many phonon modes!) I’m sure many other people have figured this out too. I wrote this paper for a grad-school course on AMO physics (“Physics 238” at UC Berkeley).