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PN Junction and Diode Energy Band Diagrams
- 1. PN junction and PN junction Diode Munira Sultana
- 2. A p–n junction is a boundary or interface between two types of semiconductor material, p-type and n-type, inside a single crystal of semiconductor. Definition
- 3. Russell Ohl discovers the p-n junction and photovoltaic effects in silicon that lead to the development of junction transistors and solar cells. In the mid-1930s Russell Ohl, an electrochemist at Bell Telephone Labs in Holmdel, NJ, began investigating the use of silicon rectifiers as radar detectors. He found that increasing the silicon purity helped improve their detection ability. On 23 February 1940, he tested a small silicon slab that yielded strange, surprising results. When exposed to bright light, the current flowing through the slab jumped appreciably. He also noticed that different parts of the crystal yielded opposite electrical effects when tested with a "cat's whisker" style probe. History
- 4. Energy Band of Semiconductor Conduction Band Valance Band 2d Band 1st Band Si 1S2 2S2 2P6 3S2 3P2 Core electrons Valance electrons Energy Band Electrical Structure
- 5. Fermi Level of Semiconductor "Fermi level" is the term used to describe the top of the collection of electron energy levels at absolute zero temperature.
- 6. N-type Doping Doping element has one valance electron more than Si. The fifth electron is loosely bound to Si, the binding energy is about 0.045ev. At slightly elevated temperatures this extra electron becomes disassociated from its atom.
- 7. Donor Level Donor level and fermi energy level at 0 k The distance between the donor level and the conduction band represents the energy that is needed to transfer the extra electrons into the conduction band EF ED
- 8. Acceptor Electrons & Level P-type doping with group (lll) impurities. The distance between the donor level and the conduction band represents the energy that is needed to transfer the extra electrons into the conduction band EF ED
- 9. PN Junction Solar Cell Metal Contacts N-type buffer P-type absorber TCO Substrate Metal-semiconductor TCO – n type buffer layer n type buffer – p type absorber layer P type absorber – TCO TCO
- 10. Metal-Semiconductor Energy bands for a metal and an n-type semiconductor (a) before and (b) after contact
- 11. Metal-Semiconductor Energy bands for a metal and an p-type semiconductor (a) before and (b) after contact
- 12. Semiconductor- Semiconductor p-n junction p-i-n junction p-n hetero-junction
- 13. PN Junction EG EG EC Ev EC EC Ev Ev P-type N-type Band Profile
- 14. P-i-N Junction EC EC EC Ev Ev Ev Ev EC P-type Intrinsic N-type Band Profile EG EG EG
- 15. P-N Hetero-Junction EG1 EG2 EC EC EC Ev Ev Ev P-type N-type Band Profile
- 16. N-N Hetero-Junction ITO/CdS hetero-junction energy band diagram
- 17. CdTe Band Profile Ag paste 3.7 ev 2.4 ev ITO CdS CdTe Graphite Ag 1.45 ev Cu, Graphite CdTe CdS Glass ITO 500nm 100nm 300nm Back Contact 20nm 40nm
- 18. Electron Reflector The use of electron reflector is a strategy to improve the open- circuit voltage of CdTe solar cells. This layer reduces the carrier recombination at the back contact. The electrons will be reflected at the CdTe/ZnTe interface and they will collected with a higher probability at the CdS/CdTe hetero- junction.
- 19. CIGSe Total Band Diagram
- 20. Thank you
Editor's Notes
- "Fermi level" is the term used to describe the top of the collection of electron energy levels at absolute zero temperature. Band gap, Egap, is the energy difference between the valence band and the conduction band
- In order to illustrate the repelling force of an external negative charge, it is customary to curve the electron energy bands upward near the surface.