Study On Measurement Of Key Properties Of Silicon Wafer And Silicon Solar Cell Using Photocarrier Radiometry(PCR) And Lock-in Photoluminescence(LIPL)

As the most widely used semiconductor material,silicon plays an important role in semiconductor chips,microelectronic devices and photovoltaics.As the increasing of the performance of semiconductor chips and the demand for solar cell power generation,the quality requirements of the design and manufacturing of silicon wafers and silicon solar cells are becoming higher and higher.The accurate detection and evaluation of the carrier transport characteristics of silicon wafers and the electrical properties of silicon-solar cells have become an important part of quality controling.Therefore,it is of great significance to develop a reliable non-destructive testing technology to accurately characterize and evaluate the performance of silicon wafers and silicon solar cells.Lock-in carrierography/photolunminescence(LIC/LIPL)is an optical and noncontact detection technology that combines lock-in method with photoluminescence method(PL).LIPL is based on an infrared camera detection which is developed from Photocarrier Radiometry(PCR),a single-element area detection method.Compared to photoluminescence,PCR/LIPL has the advantages of frequency domain dynamic responses,free-calibration and high signal-to-noise ratio,which could provide a new method for quantitative evaluation of semiconductor material performance parameters.Based on PCR/LIPL technology,the carrier density wave models of silicon wafer and silicon solar cell,effects of electrical performance parameters of solar cells on luminescence intensity,PCR/LIPL system,and obtaining carrier parameters and electrical parameters were studied in detail.One-dimensional PCR homodyne and heterodyne signal models for a one-layer silicon wafer and a one-dimensional PCR signal model for a two-layer solar cell were established.In addition,PCR signal based on an effecitive carrier lifetime model for a silicon wafer was bulit.Effects of optical parameters,structural parameters and carrier transport parameters on PCR frequency domain signals were simulated and analyzed.The sensitive range of homodyne PCR and heterodyne PCR signals on carrier transport parameters was analyzed through sensitivity simulation.A system of lock-in photoluminescence simultaneously with photocarrier radiometery was developed which integrated the homodyne and heterodyne modes of PCR and LIPL.A software based on Labview software to realize functions of data acquisition,processing and display was made.This system can realize the determination of carrier parameters of wafers and solar cells as well as electrical parameters.Effective lifetime,dopant concentration and resistivity of an n-type and p-type silicon wafer were obtained using this system.The results using PCR/LIPL are in good agreement with the results using the four-probe method.Homodyne PCR,heterodyne PCR and heterodyne LIPL methods were used to determine the bulk lifetime and surface recombination velocity of silicon wafers.Results by three methods are consistent with the result using Microwave reflectance Photoconductance Decay.Futhermore,images of bulk lifetime and surface recombination velocity at different times of the silicon wafers after etching were obtained using heterodyne LIPL.The photoelectric radiation theory of solar cells at illumination condition was analyzed,and the relationship between electrical parameters,luminescence intensity and excess carrier concentration was obtained.Based on the finite element simulation method,a two-dimensional structure model of solar cell was established.The effects of saturation current,series resistance,shunt resistance and broken finger distributions on electrical parameters and the luminescence distributions at different working conditions were analyzed.Measurements of electrical performance parameters(open circuit voltage,saturation current,and series resistance)of a c-Si solar cell and a mc-Si solar cell were carried out using LIPL.Physical mechanism of modulation by relay and laser was analyzed and understood.Eletrocal parameters results by LIPL are consistent with the results by PL.Measurements and the evaluation of performance of c-Si silicon solar cells irradiated by different energies and fluences of electron/proton were carried out.The influence of radiation energy and fluence on carrier transport parameters was analyzed using PCR.Electrical parameters based on carrier transport characteristics of irradiated solar cells were studied.The electrical parameters by PCR were in good agreement with the electrical measurements.Diffusion length maps before and after irradiation of the c-Si silicon solar cells are obtained by PCR scanning.The effect of electron fluence on the saturation current density and series resistance of c-Si solar cells was studied using LIPL.Results shows that PCR and LIPL could provide a technical means for the evaluation of the global and local carrier transport parameters and electrical parameters of irradiation solar cells.