GT6521 Solar Cell Basic Characteristics Tester At present, 70% of the energy consumed by humans comes from fossil fuels such as coal, oil and natural gas. Under the current technical conditions, the massive use of fossil energy has caused serious damage to the global environment, and the human living space has been greatly threatened. Scientists predict that although fossil fuel energy will still have a large proportion in the future, its unification of the world will gradually end (the fossil fuel formed on the earth 200 million years ago, generally only enough for humans to use for more than 300 years), renewable clean energy can be Hope to support half of the future world energy supply. The use and research of solar energy is one of the key topics in the development of new energy in the 21st century. At present, in addition to satellites and spacecrafts, silicon solar cell applications have been applied in many civilian fields: solar vehicles, solar yachts, solar radios, solar computers, solar power stations, etc. Solar energy is a clean, "green" energy source. Therefore, countries around the world attach great importance to the research and utilization of solar cells. The purpose of this experiment is to explore the basic characteristics of solar cells, which can absorb the energy of light and convert the absorbed photon energy into electrical energy. This experiment will measure the following characteristics of solar cells: 1. Measure the volt-ampere characteristic curve of the solar cell during forward bias when there is no light. 2. Measure the output characteristics of the solar cell during illumination and obtain its short-circuit current (ISC), open circuit voltage (UOC), maximum output power Pm, and fill factor FF [Pm/(IscUoc)] The fill factor is an important parameter that represents the performance of solar cells. 3, lighting effects: a. Measure the relationship between the short-circuit current ISC and the output power P, and draw a relationship diagram between ISC and P. b. Measure the relationship between the open circuit voltage UOC and the output power P, and plot the relationship between the UOC and the output power P. First, the principle The solar cell can be regarded as a diode when there is no light. The relationship between the forward bias U and the passing current I when there is no light is: (1) In the formula (1), I is a current passing through a diode, I0 and β are constants, and I0 is a reverse saturation current. From the semiconductor theory, the diode is mainly composed of a semiconductor having an energy gap of EC-EV, as shown in FIG. EC is a semiconductor ribbon, and EV is a semiconductor valence band. When the incident photon energy is greater than the energy gap, the photons are absorbed by the semiconductor, creating electron and hole pairs. The electron and hole pairs are respectively affected by the electric field inside the diode to generate a photocurrent. Assume that the theoretical model of a solar cell consists of an ideal current source (a current source that produces photocurrent from illumination), an ideal diode, a shunt resistor RSh, and a resistor RS, as shown in Figure 2. In Figure 2, IPh is the equivalent power supply output current of the solar cell when it is illuminated, and the Id is the light when it passes through the solar energy. figure 1 The current of the internal diode of the battery. From Kirchhoff's law: figure 2 (2) In the formula (2), I is the output current of the solar cell, and U is the output voltage. Available from (1), (3) Assuming that RSh = ∞ and RS = 0, the solar cell can be simplified to the circuit shown in Figure 3. Here, In the case of a short circuit, U=0, And when it is open, I=0, image 3 (4) The equation (4) is a relational expression between the open circuit voltage UOC of the solar cell and the short-circuit current ISC in the case of RSh=∞ and RS=0. Where UOC is the open circuit voltage, ISC is the short circuit current, and I0, β are constant. Second, experimental instruments and materials 1. Optical bench and slider holder; 2. Boxed solar cells with lead-out wiring; 3, digital multimeter 2, only one resistance box; 4. One optical power meter and one adjustable DC power supply; 5. One position adjustable white light source, spotlight structure, power 60W; 6, one hood. The experimental setup is shown in Figure 4. Figure 4 Third, the experimental content 1. The U-I characteristic (DC bias voltage from 0 to 3.0 V) when the solar cell is forward biased is measured without illumination (all black). a. Draw a measurement circuit diagram. b. Using the measured U-I relationship data for forward bias, draw a U-I curve. 2. When not biased, use a light source to measure the characteristics of the solar cell. Note that the distance from the source to the solar cell is now 20 cm. a. Draw a measurement circuit diagram. b. Measure the relationship between I and U under different load resistances of the battery, and draw a U-I curve. c. Find the short-circuit current ISC and the open circuit voltage UOC. d. Find the maximum output power and voltage of the solar cell. e. Calculate the fill factor FF=Pm/(Isc·Usc). 3. Measure the illumination effect and photoelectric properties of solar cells. Use a hood to block light, take the horizontal distance of the solar cell and the white light source 20cm as the starting position, measure the optical power P0 at the place with the optical power meter, the light intensity is the standard intensity J0; change the distance X of the solar cell to the light source, use the light The power meter measures the optical power P at X, the light intensity is J, and the relative intensity of the light is J/J0, that is, P/P0, and the relationship between the optical power P and the position X can be obtained. When measuring the solar cell's different optical power values, the corresponding values ​​of ISC and UOC can be obtained. a. Describe the relationship between ISC and optical power P, and find the approximate relationship function between ISC and optical power P. b. Describe the relationship between UOC and optical power P, and find an approximate function relationship between UOC and optical power P. Fourth, the experimental steps and test examples 1. In the case of full darkness, measure the current I flowing through the solar cell under forward bias of the solar cell and the output voltage U of the solar cell. The measurement circuit is shown in Figure 5, taking care not to connect the positive and negative polarity. The forward bias voltage is from 0 to 3.0 V, and the measurement results are shown in Table 1. R=1000Ω Table 1 volt-ampere characteristics of solar cells with external bias voltage in full dark condition Figure 5 U1(V) 1.9 2 2.1 2.2 2.3 2.4 U2(V) 0.2185 0.2694 0.327 0.396 0.479 0.581 I(mA) 218.5 269.4 327 396 479 581 From (I/I0)=eβU-1, when U is large, eβU>1, that is, 1nI=βU+1nI0 is processed by the least squares method, and the last 6 points of data in Table 1 are processed: β=2.60V-1, I0=6.28×10-6mA Correlation coefficient r = 0.9915. 2. When no bias is applied, the distance between the white light source and the solar cell is kept at 20 cm under the condition of using a hood, and the relationship between the output I of the solar cell and the output voltage U is measured, as shown in FIG. The short-circuit current ISC=3.5 mA and the open circuit voltage UOC=3.70 V are obtained from FIG. When the solar cell is illuminated, the output power P=I×U is related to the voltage U, as shown in FIG. 7 . Figure 6 Relationship between solar cell output current I and voltage U under illumination Figure 7 Relationship between output power P and voltage U under certain illumination From Fig. 8, the maximum output power Pmax = 6.9 mw can be obtained. At this time, the voltage U = 2380 mV, and the filling factor FF = Pm / Isc · Uoc = 6.9 / 3.5 × 3.7 = 0.533. 3. Measure the relationship between solar cell ISC and UOC and optical power P. The measurement results are shown in Fig. 8 and Fig. 9. Figure 8 Figure 9 The approximate function relationship between ISC and UOC and optical power P is found in Fig. 8 and Fig. 9 as ISC=A (J/J0) +C (5) UOC=β(J/J0)+C (6) Using least squares fitting, ISC= 6.814(J/J0) - 0.0905, correlation coefficient Outdoor Leisure Chairs,Leisure Lounge Chairs,Sunday Leisure Chair,Folding Leisure Chairs BOSA FURNITURE CO.,LTD. , https://www.bosafurniture.com =0.9996; UOC=0.5057In(J/J0)+C, correlation coefficient
=0.922. From the least squares fitting, it can be seen that the relationship between the short-circuit current ISC and the open-circuit voltage UOC is satisfied by the equations (5) and (6).