The input and output characteristic curve of a photovoltaic cell is a curve that reflects the relationship between the output voltage, current and output power of the photovoltaic cell when the sunlight shines on the photovoltaic cell. In this figure, the current is represented by I, and the voltage is represented by V. Therefore, this curve is also called the I-V characteristic curve of the photovoltaic cell.
Figure 1 is the input and output characteristic curve of the photovoltaic cell. There are many types and sizes of photovoltaic cells. How to measure their photoelectric conversion ability? ? Through the input and output characteristic curve, we can see the strength and weakness of the photovoltaic cell’s photoelectric conversion ability, so that the quality of a photovoltaic cell can be measured.
Several main performance parameters in the input-output characteristic curve of photovoltaic cells are as follows.
(1) Short-circuit current (ISC) When the positive and negative electrodes of the photovoltaic cell are short-circuited, V=0, the current at this time is the short-circuit current of the photovoltaic cell, and its unit is A (ampere), and the short-circuit current varies with the change of light intensity. Variety. In addition, the current per unit area of photovoltaic cells is called short-circuit current density, and its unit is A/m² or mA/mm².
(2) Open-circuit voltage (Voc) When the positive and negative poles of the photovoltaic cell are not connected to the load and are in an open-circuit state, the voltage between the positive and negative poles of the photovoltaic cell is the open-circuit voltage, and the unit of the open-circuit voltage is V (volts). The open circuit voltage of a single photovoltaic cell does not change with the increase or decrease of the cell area, and is generally 0.5~0.7V. When multiple photovoltaic cells are connected in series, a higher voltage can be obtained.
(3) Peak current (Im) The peak current is also called the maximum working current or the optimal working current. As the name implies, it is the working current when the photovoltaic cell outputs the maximum power, and its unit is A.
(4) Peak voltage (Vm) The peak voltage is also called the maximum working voltage or the best working voltage, that is, the working voltage when the photovoltaic cell outputs the maximum power, and its unit is V. The peak voltage does not change with the increase or decrease of the photovoltaic cell area, generally 0.45~0.55V, and the typical value is 0.48V.
(5) Peak power (Pm) Peak power, also known as maximum output power or optimal output power, refers to the optimal output power of photovoltaic cells under normal working or test conditions, that is, the product of peak current and peak voltage, and its unit is WP (peak watts). The peak power of photovoltaic cells depends on solar irradiance, solar spectral distribution and the operating temperature of photovoltaic cells. Therefore, the measurement of photovoltaic cells should be carried out under standard conditions. The measurement standard is the European Commission’s No. 101 standard, and its conditions are: 1000W /m² or 100mW/cm²: Spectrum AM1.5: Test temperature 25℃