E_n-I_n Noise Model Establishment And Reliability Screening Methods Study For Solar Cells

With the wide application of solar cells in human society, especially as an importantpart of the power supply system used in the field of high precision, such as the orbit spacestation, spacecraft and satellites and other spacecraft power supply and the environment isvery different from that in which solar cells are produced and tested, since solar cells are putinto use, the research on their reliability study is always ongoing.Low-frequency noise as an efficient, non-destructive method has been used as an im-portant tool for the reliability analysis of semiconductor devices. Low-frequency noise gen-erates from the irregular movement of the internal carrier in semiconductor device, and isinevitable. It has been obtained that the extreme low-frequency noise is an important indica-tor of the characterization of device reliability. At present, it has been found that the maintypes of extreme noise existed in the solar cell are1/f noise, GR noise, RTS noise and burstnoise, and the latter three types of low-frequency noise in the frequency domain expressed asthe G-R spectrum, while the RTS noise and burst noise are specially expressed as pulse se-quences made up with different duration and same amplitude pulsed in the time domain.Although the reliability screening methods of solar cells based on low-frequency noisefilter have some preliminary researches, there still exits some problems as follows to besolved from reading the extensive literature:(1) although there is a certain understanding ofthe low-frequency noise in solar cells, the what shape the noise signal expresses as, voltageor current, have not been studied, and also how the different shape noise in solar cells disturbits two important parameters which are short-circuit current and open-circuit voltage, the es-tablishment of a noise model for solar cells is needed;(2) the extraction method of voltagenoise and current noise in solar cells has not been studied;(3) for the reliability study of thewidely used solar modules is limited to visual observation, or measurement of parameterssuch as the open circuit voltage, short circuit current and a long period of stress experiments,while the non-destructive, convenient, efficient method based on low-frequency noise forsolar cells reliability estimation are little studied;(4) it is still blank in the field of noise pa-rameters study of the solar modules which are common used in practical applications.Therefore, considering the short-circuit current and open circuit voltage influenced by the low-frequency noise in solar cells, establish the E_n-I_n noise model and extract its noiseparameters, comparing all the measured noise parameters, study the reliability screeningmethod, and study the noise parameters of solar cell modules with the basis of the single so-lar cell noise model in order to obtain the modules reliability assessment method based onthe low-frequency noise, which is essential. Therefore, the following aspects are studied inthis paper:(1) Build the equivalent two-port network of the solar cells and extract the E_n-I_n noisemodelBuild the equivalent two-port network of solar cells according to the solar cells equiva-lent circuit; analyze the low-frequency noise types of the solar cells and the noise generationmechanisms, then obtain the two-port network in which the internal noise sources areequivalent to the output as the forms of current noise source and voltage noise source, at last,extract the E_n-I_n noise model of solar cells.(2) Study the extraction and measurement methods of parameters of solar cell E_n-I_nnoise modelConsidering the noise power caused by the internal or surface defects in solar cells isequivalent to the output noise power according to the two-port network theory, study the re-lationship between the noise parameters of current noise and voltage noise and the outputnoise power, then obtain the two noise parameter extraction methods; design the actual testcircuits based on the noise parameter extraction methods.(3) Study the reliability screening methods of the solar cellAnalysis the components of the current noise power spectrum and voltage noise powerspectrum, extract the frequency range and frequency index of1/f spectral composition andthe corner frequency and amplitude of G-R spectral composition. Then find the characteristicfrequency-point noise and the full-band frequency parameter as the basis for solar cells reli-ability screening. The most sensitive frequency point in the1/f spectrum frequency band andthe G-R spectrum amplitude are chosen as the two sensitive parameters for the reliabilityscreening and sorting; while take into account that the above two point-frequency noise cannot represent information completely, so in order to get more detailed and accurate sortingresults, the Gower similarity coefficient is chosen as a sensitive parameter of the full fre-quency band, and use the one by one classification method for the reliability of sorting.(4) Study the calculation method of noise parameters in the simple dual-connected solarcell modules This paper only considers the simple components composed of only two solar cellsconnected with the form of series or parallel, study the methods of the network noise pa-rameters calculation methods respectively, and then obtain the general law for the furtherstudy of the complex solar cell modules’ noise characteristics.