Introduction to Semiconductors Katherine Rinaldi (Slides by Fadl Saadi) SEAL 9/29/2017

CCI Solar: The story Converting the sun’s energy into chemical bonds by making molecules. Harvest energy from these molecules.  Fuels from the sun hν 2H2O 2H2 + O2 Electrons protons. Like burning gas. Methane. Methanol is one of our goals. Hydrogen, simplest chemical bond

Semiconductor Basics Convert the energy in sunlight to electrical energy. Why fto picture? What are the white circles? What are the black dots? Why depicted like this?

Semiconductor Uses

Semiconductor Basics Convert the energy in sunlight to electrical energy. Why fto picture? What are the white circles? What are the black dots? Why depicted like this?

Semiconductor Basics Shining light on a semiconductor is like placing a ball at the top of a hill Convert the energy in sunlight to electrical energy. Why fto picture? What are the white circles? What are the black dots? Why depicted like this?

Semiconductor Basics This ball could do work for us by, say, knocking over dominoes at the bottom of the hill Energy from an electron in a solar cell is like that of a ball rolling down a hill. Convert the energy in sunlight to electrical energy. Why fto picture? What are the white circles? What are the black dots? Why depicted like this?

Semiconductor Basics Energy Needed to Split Water Why fto picture? What are the white circles? What are the black dots? Why depicted like this?

Semiconductor Basics Energy Needed to Split Water Why fto picture? What are the white circles? What are the black dots? Why depicted like this? The semiconductor needs to have the right bandgap (or ‘hill height’) for the reaction to take place.

Why not just pick a really high hill? Semiconductor Basics Energy Needed to Split Water Why fto picture? What are the white circles? What are the black dots? Why depicted like this? Why not just pick a really high hill?

Semiconductor Basics Transition State Energy Needed to Split Water Why fto picture? What are the white circles? What are the black dots? Why depicted like this?

Semiconductor Basics Transition State Energy Needed to Split Water Why fto picture? What are the white circles? What are the black dots? Why depicted like this?

Semiconductor Basics Transition State Energy Needed to Split Water Why fto picture? What are the white circles? What are the black dots? Why depicted like this? A catalyst helps lower the energy barrier and lets the reaction take place faster!

Questions?