The role of solar module EL tester in solar cell production

- Jul 02, 2018-

The solar module EL tester, which can also be called an electroluminescence tester, is a method that utilizes near-infrared detection, and detects common recessiveness in crystalline silicon solar cells and modules by powering a cell sheet or a component. The defect detection equipment plays an important role in the production and production of solar modules.


With the rapid development of the photovoltaic industry, the testing methods in the quality control of solar modules have been continuously enhanced, and the original appearance and electrical performance tests have been far from meeting the needs of the industry. At present, a method that can test potential defects of solar cells and modules is widely used in the industry. It is a solar module EL tester.


In solar cells, the diffusion length of the minority is much larger than the barrier width, so the probability of electrons and holes disappearing due to recombination as they pass through the barrier region is small, and diffusion continues to the diffusion region. Under the forward bias voltage, the pn junction barrier region and the diffusion region are implanted with minority carriers. These non-equilibrium minority carriers continuously recombine with the majority carrier to emit light. This is the basic principle of electroluminescence in solar cells. .


By adding a forward bias across the solar cell, the photons emitted by it can be obtained by a sensitive infrared camera, but the electroluminescence intensity is very low, and the wavelength is in the near-infrared region, requiring the camera to have high sensitivity at 900-1100 nm. And very little noise.


The testing process of the solar module EL tester is actually a forward bias voltage applied to the solar cell. The DC power supply injects a large amount of non-equilibrium carriers into the crystalline silicon solar cell, and the solar cell relies on a large amount of non-equilibrium carriers injected from the diffusion region. The compound emits light and emits photons; these photons are captured by an infrared camera, processed by a computer and displayed in the form of images. The entire process is performed in a dark room.


Because the brightness of the image tested by the solar module EL tester is proportional to the minority son lifetime and current density of the solar cell, the defect length of the minority son in the solar cell has a low diffusion length, and thus the brightness of the displayed image is dark. Therefore, through the analysis can be clearly found in solar cells and components of hidden defects.