4. (25 marks) Compose a short essay outlining everything you know about one of the topics listed below.
Important points to consider when preparing your essay:
–    Your short essay must be between 2 and 3 typed pages in length (12pt Times font, 2.54 cm margins all around, 1.5 line spacing).
–    For any essay longer than 3 pages, excess pages will be removed and not considered in graded. 
–    Unlike for the rest of the exam, you are free to include figures/diagrams taken directly from lecture notes (no other source will be accepted), however these diagrams must be numbered sequentially, have appropriate meaningful captions that are inserted using the caption function, and be referred to in the body text of the essay.
–    Essays should include discussion related to material/device preparation, structure, explanation of properties, and applications.
–    Figures/diagrams in the text and do not contribute to the page length. 
–    This question will be marked on depth of understanding, clarity of writing, formatting (e.g., subscripts and superscripts), as well as spelling and grammar.

Topic:
OLEDS