Show that the built-in potential V bi is given by: M a x V oc = V bi = e k T ln n i 2 n p For a silicon solar cell with the hole concentration of 1 × 1 0 17 / cm 3 on the p side and electron concentration of 1 × 1 0 16 / cm 3 on the n side, calculate the theoretical maximum open-circuit voltage at room temperature for this silicon solar cell, given that n i 2 = 2 × 1 0 20 / cm 6 and kT / e = 0.026 volt at room temperature. Derive the following expression: V oc = e k T ln ( 1 + I o I sc ) b) The maximum open-circuit voltage for a solar cell is limited by the built-in potential. a) Define the open-circuit voltage V oc as V ( I = 0 ) and short-circuit current I sc as ∣ I ( V = 0 ) ∣. The EL7900 senses ambient-light intensity and outputs a current proportional to this intensity. Lastly, we plug in our given values and solve. Next, we rearrange the equation to solve for wavelength. The reason for the negative sign in front of α G is that the current produced by light excitation is opposite to the current direction under forward bias condition. We can start with our equation that relates frequency, wavelength, and the speed of light. The diode equation is modified allows: I ( V ) = I o − α G where G is the light intensity and α the overall efficiency factor in converting photon flux into electric current. When light with energy greater than the oandgap of silicon falls onto this solar cell, electron-hole pairs are created, which then separate under the electric field at the p n junction to produce a current. Consider a silicon p n junction operating as a solar cell. Highly inaccurate with a response time of about tens or hundreds of milliseconds. Luminous intensity is defined as dId / d, where d is the luminous flux (light energy flux in watts per m2) emitted within a solid angle d. ![]() They need very small power and voltage for its operation. Practical LDRs are available in a variety of sizes and package styles, the most popular size having a face diameter of roughly 10 mm. LDR’s are cheap and are readily available in many sizes and shapes. The value of ‘a’ depends on the CdS used and on the manufacturing process. The passive component is basically a resistor whose resistance value decreases when the intensity of light decreases. It is basically a photocell that works on the principle of photoconductivity. The equation to show the relation between resistance and illumination can be written as A Light Dependent Resistor (LDR) is also called a photoresistor or a cadmium sulfide (CdS) cell. This causes the free electrons or holes to conduct electricity and thus dropping the resistance dramatically (< 1 Kiloohm). When the light intensity exceeds a certain frequency, the photons absorbed by the semiconductor give band electrons the energy required to jump into the conduction band. ![]() As soon as light falls on the sensor, the electrons are liberated and the conductivity of the material increases. In the absence of light it is designed to have a high resistance inthe range of megaohms. As explained above, the main component for the construction of LDR is cadmium sulphide (CdS), which is used as the photoconductor and contains no or very few electrons when not illuminated. The structure is housed in a clear plastic or resin case, to provide free access to external light. It is designed in such a way as to provide maximum possible contact area with the two metal films. On the top and bottom are metal films which are connected to the terminal leads. The snake like track shown below is the Cadmium Sulphide (CdS) film which also passes through the sides.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |