| The growing shortage of fossil fuels makes the development of new energy more urgent.Solar energy is a promising renewable energy with rich reserves,pollution-free and widely distributed resources.The most commonly used device for converting solar energy into electrical energy is crystalline silicon solar cells.However,various impurities or defect s exist in crystalline silicon,which generally lead to serious light-induced degradation（LID）,seriously influencing the efficiency of converting solar energy into electric energy.The light-induced hydrogen regeneration（LIHR）technology can effectively suppress the LID of crystalline silicon solar cells and further improve the conversion efficiency.Actually,many mechanisms and technologies of LIHR need to be studied to suppress the LID of crystalline silicon solar cells.Therefore,the LIHR and its effect detection technology of crystalline silicon solar cells were studied in this paper.The specific research was divided into the following aspects,（1）A LIHR platform with high brightness LED as light source was developed.The light absorption model of crystalline silicon solar cell was established,and the ideal irradiation wavelength of LIHR was determined.Based on this,a light source for LIHR was developed.The structure of the platform was designed and optimized,the temperature control,irradiance and irradiation uniformity were studied,and a novel type of LIHR platform was independently developed.The function of LIHR platform was verified by related experiments.Additionally,the function of fast LID of the platform was developed.The establishment of the platform has laid a foundation for the research of LIHR technology.（2）The LIHR and its effect detection technology of monocrystalline silicon（mono-Si）Passivated emitter and rear contact（PERC）solar cells were studied.Based on LIHR platform,the key technical parameters applicable to boron-doped mono-Si PERC solar cells were established,which were irradiance 20 Suns,temperature 240℃and time 8 min,respectively.The conversion efficiency was improved by 0.15%abs.compared with the initial value,and the LID rate was controlled at-1.0%rel..On this basis,a method of Pre-degradation（Pre-Deg.）to generate B-O complex in advance was proposed,which shortened the treatment time of LIHR to 1-2 min.The conversion efficiency was increased by about 0.17%abs.and LID rate was controlled to-0.40%rel..The configuration of B-O complex was studied,and the scheme of detecting B-O bond and O-H bond by FTIR was proposed,which further clarified the passivation mechanism of B-O complex by LIHR.The corresponding relationship between the peak intensities of B-O bond and O-H bond before and after treatment and the LIHR effect was calculated,and a novel method for detecting the effect of LIHR was established.（3）The LIHR and its effect detection technology of multi-crystalline silicon（mc-Si）PERC solar cells were studied.The key technical parameters applicable to mc-Si PERC solar cells were established,which were irradiance 22 Suns,temperature 300℃and time 8 min,respectively.The conversion efficiency was improved by 0.13%abs.compared with the initial value and the LID rate was controlled at-2.07%rel..A Pre-Deg.method for dissociating Fe-B complex in advance was proposed,reducing the LIHR time to 2-3 min,so that the conversion efficiency was improved by 0.12%abs.and the LID rate was controlled at-1.96%rel..A rapid cooling measure were established to increase the conversion efficiency by 0.15%abs.and control the LID rate at-1.51%rel..The diffusion length of carriers in silicon before and after different treatments was measured,and the concentration of interstitial Fei+was estimated,which proved that LIHR has passivation effect on interstitial Fe-B complex and interstitial Fei+.A novel detection method was established for passivation of interstitial Fei+.Moreover,the XRD detection of dislocation was established,and the dislocation density was quantified.Thus,the passivation rate of dislocation was determined,and a novel detection method for passivation effect of dislocation by LIHR was established.（4）The kinetics of charged hydrogen in LIHR was studied to further shorten the treatment time.Combined with the experimental research on the LIHR technology,the drift rate and mobility of charged hydrogen in P-type silicon were estimated.Actually,the effective life of H-was much shorter than the time it took to pass through the entire silicon wafer,the transformation of H-and H+in the P-type substrate was clarified,which revealed the reason why LIHR took a long treatment time.Then,the process of LIHR was analyzed in detail,and the motion of H-in P-type silicon substrate,the transformation between H-and H+,and the passivation of H-to defects were clarified.Meanwhile,the differences of LIHR of crystalline silicon solar cells under 445 nm and 940 nm light sources were studied,and the dynamic process of H-in P-type crystalline silicon solar cells was verified.Additionally,to further improve the passivation effect of LIHR and shorten the LIHR treatment time,an additional electric field with appropriate intensity and opposite direction to the light-generated electric field was proposed.（5）A real-time monitoring system for LIHR was developed.The relationship among open-circuit voltage(Voc),defect density and passivation effect of LIHR of crystalline silicon solar cells was studied,and Voc could be used as a parameter for real-time monitoring of LIHR effect.The method of real-time monitoring the Voc to determine the optimum time point for improving the effect of mono-Si PERC solar cells with different efficiency grades is proposed,and a real-time monitoring system for the effect of LIHR is developed,achieving the monitoring system’s detection accuracy of±3 s.Therefore,a novel method for monitoring the time point of the optimum improvement effect of LIHR was established to achieve fine control of the treatment time of LIHR.The method established in the research work of this paper has realized significant improvement in the conversion efficiency and effective suppression of LID for mono-Si and mc-Si solar cells,which provides support for the application and promotion of LIHR technology,and can also help the high-quality and high-level development of the photovoltaic industry and the realization of the goals of"carbon peak"and"carbon neutralization". |
