Study On Solar Cell Silicon Electrode Parameter Testing Based On PCR

With the continuously improving demand for sustainable clean energy, the solar photovoltaic industry has rapidly developed all over the world, while performance of solar cells, as an important device for solar power generation in civil and aerospacefield, is very important for widespread use of solar power. Performance of crystalline silicon solar cell(monocrystalline silicon and multicrystalline silicon) can be represented by silicon electron parameters including carrier transport parameters and electric parameters. silicon electron consist of of base region and emitter region. In order to test silicon electron carrier transport parameters and electric parameters, non-contact nondestructive testing technology is needed. Modulated photocarrier radiation detection(also called Laser- induced infrared photocarrier radiometry, PCR for short) is near-infrared lock-in luminescence detection method combining a carrier radiative recombination luminescence(Photoluminescence or fluorescence) with lock-in technology. PCR has advantages of non-contact, high signal-to-noise ratio and high precision, providing non-contact rapid new method for tesing silicon electron minority carrier transport and electrical parameters of crystalline silicon solar cells. In this thesis, the main content includes: non-equilibrium excess minority carrier transport model of crystalline silicon solar cells excited by modulation laser, the non-equilibrium excess minority carrier dynamic response simulation, PCR experimental system developing, PCR frequency response testing and the silicon electron transport parameter reverse in low injection condition, the unbalanced minority carrier radiation current equation and electric parameter detection for crystalline silicon solar cells.Analyze modulated laser inducing non-equilibrium excess minority carrier diffusion transport process in pn junction of crystalline silicon solar cells, build one dimensional mathematical model of non-equilibrium excess minority carrier density wave based on small AC voltage signal, and the frequency domain one-dimensional analytical result is calculated by green function method, which laid theoretical foundation for dynamic response analysis of the non-equilibrium minority carriers radiation; Building the equivalent circuit based on the AC signal analysis, combined with the non-equilibrium excess minority carrier density wave one-dimensional analytical model, the numerical simulation were calculated to analyze the effect of minority carrier transport parameters, quasi neutral zone doping concentration, bias voltage, parallel resistance and cell area on PCR dynamic characteristics. Due to effect of capacitive reactance – impedance of pn junction, the PCR signal frequency response performs double-knee feature. By increasing the bias voltage to decrease the p-n junction effect of capacitive reactance- impedance, the PCR dynamic characteristics equivalent circuit can be simplified as diode with single-knee, which is only related to the minority carrier transport parameters.Establish nonequilibrium excess minority carrier density wave three-dimensional mathematical model under the condition of high positive bias voltage, analyzing effect of laser excitation parameters, uneven distribution carrier transport parameters and integral area on non-equilibrium excess minority carrier density wave distribution and PCR frequency response by finite element analysis. Reverse method of minority carrier transport parameters were studied in two cases: uniform carrier transport parameters with one-dimensional model parameter reverse and uneven carrier transport parameters with multi-dimensional FEM reverse. Trust-Region Reflective Newton, Nelder-Mead method and simulated annealing algorithm were employed for carrier transport parameter reverse, and iteration steps and accuracy of the results were compared. Carrier transport parameters were calculated accurately by combination of location scan and frequency scan;Develop modulated laser inducing minority carrier radiation frequency domain scanning system. The system is mainly composed of semiconductor optical fiber laser, adjustment and collection light path, a two-dimensional workbench, digital lock-in amplifier, In Ga As(0.9 μm- 1.7 μm) wavelength near-infrared detector and software system based on Labview, and the system can realize carrier radiation frequency response analysis and minority carrier transport parameter detection for crystalline silicon solar cells induced by modulated laser. By PCR experimental study of monocrystalline silicon solar cell and radiation-induced damage cell, the effectiveness of excess minority carrier density wave model was verified, and silicon electron minority carrier transport parameters and solar cell doping concentration were achieved. The effect of bias voltage and light radiation parameters on the carrier frequency domain response were studied by frequency scanning experiment, which realized minority carrier transport property analysis and evaluation of crystalline silicon solar.Radiative recombination photocurrent ideal factor and short circuit collection efficiency were introduced into carrier radiative recombination photocurrent equations. Relationship between the laser inducing silicon solar cell carrier radiation signal and the solar cell electrical parameters was built based on energy conservation, photon flow conservation and. Build a PCR lock-in imaging system for modulated laser inducing silicon solar cell carrier radiation, which consists of semiconductor fiber laser, laser cosmetic and beam expander device, NI-DAQ data acquisition card, In Ga As near-infrared camera and lock-in processing software based on Labview. Whole and partial basic electrical parameters are calculated by carrier radiation current equation and the built experimental set-up.By experimental measurement using electrical measuring method and PCR imaging(also called LIP), the basic electrical parameter testing results(short circuit current density JSC, open circuit voltage VOC) for the monocrystalline silicon and multicrystalline silicon solar cell are compared with each other, which provides new methods and new technology for non-contact nondestructive testing and evaluation for the crystalline silicon solar cell performance.