The n-type silicon integrated-back contact（IBC） solar cell has attracted much attention due to its high efficiency,whereas its performance is very sensitive to the wafer of low quality or the contamination during hi...The n-type silicon integrated-back contact（IBC） solar cell has attracted much attention due to its high efficiency,whereas its performance is very sensitive to the wafer of low quality or the contamination during high temperature fabrication processing, which leads to low bulk lifetime τbulk. In order to clarify the influence of bulk lifetime on cell characteristics, two-dimensional（2D） TCAD simulation, combined with our experimental data, is used to simulate the cell performances, with the wafer thickness scaled down under various τbulk conditions. The modeling results show that for the IBC solar cell with high τbulk,（such as 1 ms-2 ms）, its open-circuit voltage V oc almost remains unchanged, and the short-circuit current density J sc monotonically decreases as the wafer thickness scales down. In comparison, for the solar cell with low τbulk（for instance, 〈 500 μs） wafer or the wafer contaminated during device processing, the V oc increases monotonically but the J sc first increases to a maximum value and then drops off as the wafer＇s thickness decreases. A model combing the light absorption and the minority carrier diffusion is used to explain this phenomenon. The research results show that for the wafer with thinner thickness and high bulk lifetime, the good light trapping technology must be developed to offset the decrease in J sc.展开更多
Hydrogenated doped silicon thin films deposited using RF (13.56 MHz) PECVD were studied in detail using micro Raman spectroscopy to investigate the impact of doping gas flow, film thickness, and substrate type on the ...Hydrogenated doped silicon thin films deposited using RF (13.56 MHz) PECVD were studied in detail using micro Raman spectroscopy to investigate the impact of doping gas flow, film thickness, and substrate type on the film characteristics. In particular, by deconvoluting the micro Raman spectra into amorphous and crystalline components, qualitative and quantitative information such as bond angle disorder, bond length, film stress, and film crystallinity can be determined. By selecting the optimum doped silicon thin film deposition conditions, and combining our p-doped and n-doped silicon thin films in different heterojunction structures, we demonstrate both (i) an efficient field effect passivation and (ii) further improvement to c-Si/a-Si:H(i) interface defect density with observed improvement in implied open-circuit voltage VOC and minority carrier lifetimes across all injections levels of interest. In particular, the heterojunction structure (a-Si:H(p)/a-Si:H(i)/c-Si(n)/a-Si:H(i)/a-Si:H(p)) demonstrates a minority carrier lifetime of 2.4 ms at an injection level of 1015 cm-3, and a high implied open-circuit voltage of 725 mV. Simulation studies reveal a strong dependence of the interface defect density Dit on the heterojunction silicon wafer solar cell performance, affected by the deposition conditions of the overlying doped silicon thin film layers. Using our films, and a fitted Dit of 5 × 1010 cm-2·eV-1, we demonstrate that a solar cell efficiency of ~22.5% can be potentially achievable.展开更多
基金Project supported by the Chinese Ministry of Science and Technology Projects(Grant Nos.2012AA050304 and Y0GZ124S01)the National Natural Science Foundation of China(Grant Nos.11104319,11274346,51202285,51402347,and 51172268)the Fund of the Solar Energy Action Plan from the Chinese Academy of Sciences(Grant Nos.Y3ZR044001 and Y2YF014001)
文摘The n-type silicon integrated-back contact（IBC） solar cell has attracted much attention due to its high efficiency,whereas its performance is very sensitive to the wafer of low quality or the contamination during high temperature fabrication processing, which leads to low bulk lifetime τbulk. In order to clarify the influence of bulk lifetime on cell characteristics, two-dimensional（2D） TCAD simulation, combined with our experimental data, is used to simulate the cell performances, with the wafer thickness scaled down under various τbulk conditions. The modeling results show that for the IBC solar cell with high τbulk,（such as 1 ms-2 ms）, its open-circuit voltage V oc almost remains unchanged, and the short-circuit current density J sc monotonically decreases as the wafer thickness scales down. In comparison, for the solar cell with low τbulk（for instance, 〈 500 μs） wafer or the wafer contaminated during device processing, the V oc increases monotonically but the J sc first increases to a maximum value and then drops off as the wafer＇s thickness decreases. A model combing the light absorption and the minority carrier diffusion is used to explain this phenomenon. The research results show that for the wafer with thinner thickness and high bulk lifetime, the good light trapping technology must be developed to offset the decrease in J sc.
文摘Hydrogenated doped silicon thin films deposited using RF (13.56 MHz) PECVD were studied in detail using micro Raman spectroscopy to investigate the impact of doping gas flow, film thickness, and substrate type on the film characteristics. In particular, by deconvoluting the micro Raman spectra into amorphous and crystalline components, qualitative and quantitative information such as bond angle disorder, bond length, film stress, and film crystallinity can be determined. By selecting the optimum doped silicon thin film deposition conditions, and combining our p-doped and n-doped silicon thin films in different heterojunction structures, we demonstrate both (i) an efficient field effect passivation and (ii) further improvement to c-Si/a-Si:H(i) interface defect density with observed improvement in implied open-circuit voltage VOC and minority carrier lifetimes across all injections levels of interest. In particular, the heterojunction structure (a-Si:H(p)/a-Si:H(i)/c-Si(n)/a-Si:H(i)/a-Si:H(p)) demonstrates a minority carrier lifetime of 2.4 ms at an injection level of 1015 cm-3, and a high implied open-circuit voltage of 725 mV. Simulation studies reveal a strong dependence of the interface defect density Dit on the heterojunction silicon wafer solar cell performance, affected by the deposition conditions of the overlying doped silicon thin film layers. Using our films, and a fitted Dit of 5 × 1010 cm-2·eV-1, we demonstrate that a solar cell efficiency of ~22.5% can be potentially achievable.
