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Introduction to Semiconductor elect (1).pdf
- 2. WHAT IS SEMICONDUCTOR ELECTROCHEMISTRY Semiconductor electrochemistry is a field that studies the electrochemical properties of semiconductors and their applications in various fields such as energy conversion, environmental remediation, and sensing. It involves the study of the interaction between light, electrons, and chemical reactions at the surface of semiconductors.
- 3. BASIC PRINCIPLE Semiconductors are materials that have electrical conductivity between that of metals and insulators. They have a band gap, which is the energy difference between the valence band and the conduction band. When light is absorbed by a semiconductor, electrons are excited from the valence band to the conduction band, creating electron-hole pairs. These electron-hole pairs can participate in electrochemical reactions at the surface of the semiconductor.
- 4. . METAL CONTACTS AND P-N JUNCTIONS SOLID STATE DEVICES GENERALLY REQUIRE METALLIC CONTACTS. THE BEHAVIOR OF THESE CONTACTS IS NOT ALWAYS PREDICTABLE DUE TO THE PRESENCE OF INTERMEDIATE LAYERS, BUT IN PRINCIPLE THE TYPE OF CONTACT DEPENDS ON THE ELECTRONIC WORK FUNCTIONS OF THE SEMICONDUCTOR AND THE METAL. FORMATION OF THE CONTACT INVOLVES ESTABLISHING ELECTRONIC EQUILIBRIUM, SO THAT THE FERMI LEVELS IN THE METAL AND THE SEMICONDUCTOR MUST BE EQUAL AFTER CONTACT. DURING THE EQUILIBRATION PROCESS, ELECTRONS ARE TRANSFERRED ACROSS THE JUNCTION AS SHOWN, FOR EXAMPLE, IN FIGURE 2 FOR AN N-TYPE SEMICONDUCTOR IN CONTACT WITH A METAL THAT HAS A HIGHER WORK FUNCTION (LOWER FERMI LEVEL). IN THIS CASE, THE EQUILIBRATION OF THE FERMI LEVELS RESULTS IN FORMATION OF A SCHOTTKY BARRIER, GIVING RISE TO DIODE BEHAVIOR. IF THE WORK FUNCTION OF THE METAL IS LOWER THAN THAT OF THE N-TYPE SEMICONDUCTOR, ELECTRONS FLOW IN THE OPPOSITE DIRECTION, AND AN OHMIC CONTACT IS FORMED. IN THE CASE WHERE A SCHOTTKY BARRIER IS FORMED, THE REMOVAL OF MAJORITY CARRIERS (ELECTRONS) FROM THE SEMICONDUCTOR GIVES RISE TO A REGION WHERE THE IONIZED DONOR ATOMS IN THE LATTICE CONSTITUTE AN IMMOBILE SPACE CHARGE. THE WIDTH OF THIS SPACE CHARGE REGION DEPENDS ON THE DOPING LEVEL, TYPICALLY RANGING FROM 1 MICRON TO 10 NM FOR DOPING DENSITIES OF 1021 TO 1025 M-3 RESPECTIVELY
- 5. APPLICATIONS OF PHOTOELECTROCHEMISTRY SOLAR ENERGY CONVERSION: PHOTOELECTROCHEMICAL CELLS CAN BE USED TO CONVERT SOLAR ENERGY INTO ELECTRICAL ENERGY.WATER SPLITTING: PHOTOELECTROCHEMICAL CELLS CAN BE USED TO SPLIT WATER INTO HYDROGEN AND OXYGEN, WHICH CAN THEN BE USED AS FUEL.ENVIRONMENTAL REMEDIATION: PHOTOELECTROCHEMICAL CELLS CAN BE USED TO REMOVE POLLUTANTS FROM WASTEWATER.
- 6. PHOTOELECTROCHEMISTRY PHOTOELECTROCHEMISTRY IS THE STUDY OF THE INTERACTION BETWEEN LIGHT AND ELECTROCHEMICAL PROCESSES IN SEMICONDUCTORS. WHEN A SEMICONDUCTOR IS EXPOSED TO LIGHT, IT GENERATES ELECTRON-HOLE PAIRS WHICH CAN BE USED FOR VARIOUS ELECTROCHEMICAL REACTIONS. PHOTOELECTROCHEMICAL CELLS A PHOTOELECTROCHEMICAL CELL IS A DEVICE THAT UTILIZES LIGHT TO GENERATE AN ELECTRICAL CURRENT. THIS IS ACHIEVED THROUGH A PHOTOANODE AND A CATHODE, WHICH ARE TYPICALLY MADE OF SEMICONDUCTING MATERIALS.
- 7. SENSORS SEMICONDUCTOR ELECTROCHEMISTRY HAS ALSO BEEN USED IN THE DEVELOPMENT OF SENSORS, WHICH DETECT AND MEASURE THE CONCENTRATION OF VARIOUS SUBSTANCES IN A SAMPLE. FOR EXAMPLE, SEMICONDUCTOR GAS SENSORS CAN DETECT THE PRESENCE OF GASES SUCH AS CARBON MONOXIDE, NITROGEN OXIDES, AND HYDROGEN. THESE SENSORS HAVE APPLICATIONS IN AIR QUALITY MONITORING, INDUSTRIAL SAFETY, AND MEDICAL DIAGNOSTICS.
- 8. SOLAR ENERGY CONVERSION SEMICONDUCTOR ELECTROCHEMISTRY HAS BEEN APPLIED IN THE DEVELOPMENT OF SOLAR CELLS, WHICH CONVERT SUNLIGHT INTO ELECTRICAL ENERGY. IN THESE CELLS, SEMICONDUCTORS ABSORB LIGHT AND GENERATE ELECTRONS THAT ARE COLLECTED BY ELECTRODES TO PRODUCE ELECTRICITY. THIS TECHNOLOGY HAS THE POTENTIAL TO PROVIDE A CLEAN AND RENEWABLE SOURCE OF ENERGY.
- 9. WATER SPLITTING SEMICONDUCTOR ELECTROCHEMISTRY HAS ALSO BEEN APPLIED IN THE PROCESS OF WATER SPLITTING, WHICH INVOLVES USING ELECTRICITY TO SPLIT WATER INTO HYDROGEN AND OXYGEN. THIS TECHNOLOGY HAS THE POTENTIAL TO PROVIDE A CLEAN AND RENEWABLE SOURCE OF HYDROGEN FUEL, WHICH CAN BE USED IN FUEL CELLS TO GENERATE ELECTRICITY.
- 10. SEMICONDUCTOR ELECTROCHEMISTRY IN FUEL CELLS BASED ON THE FUNDAMENTALS OF SEMICONDUCTOR ELECTROCHEMISTRY BRIEFLY DISCUSSED IN THE ABOVE SECTION, WE FURTHER DISCUSS BOTH CONVENTIONAL ION-BASED ELECTROLYTES AND SEMICONDUCTOR-BASED MEMBRANES FOR FUEL CELLS, WITH AN EMPHASIS ON HOW SEMICONDUCTOR-IONIC CONDUCTORS REPLACE CONVENTIONAL IONIC ELECTROLYTES, RESULTING IN DIFFERENT SCIENTIFIC PRINCIPLES.