Study On Passivation Contact Technology Of Silicon Thin Film In N-type Crystalline Silicon Solar Cell

The increasing demand for energy and the limited supply of energy have begun to restrict the development of the world economy,energy issues have drawn more and more attention,so people have turned their attention to new,clean and renewable green energy.The photovoltaic utilization of solar energy has become the fastest and most dynamic research field in recent years.In this paper,on the basis of high efficiency crystalline silicon solar cells,n-type poly-Si Cx thin films were applied as the window layer of the cells.The effect of different carbon doping ratios R[methane flow（sccm）/silane flow（sccm）]and the annealing temperatures on the passivation quality was investigated.A series of poly-Si Cx films with different carbon contents were prepared by PECVD（plasma-enhanced chemical vapor deposition）.The microstructure and optical property of poly-Si Cx films was studied by Raman spectra,X-ray photoelectron spectroscopy and UV-VIS spectrophotometer;Lifetime measurements were carried out using the Sinton WCT-120 Lifetime Test Instrument;the test results show that the:The carbon doping ratios R and annealing temperature have great influence on the microstructure and passivation effect of poly-Si Cx films prepared by plasma-enhanced chemical vapor deposition.The text results of XPS indicate that the peak of Si-C mode became stronger with the increase of carbon content.The text results of Raman showed that the incorporation of carbon lowered the crystalline fraction of poly-Si Cx and a higher annealing temperature was needed to achieve high crystallinity.The lifetime test showed that,given a lower annealing temperature,the passivation quality of poly-Si Cx thin films was very poor at R over 0.2,and it can be improved by elevating the annealing temperature.The effective lifetime of over 1.8ms can be obtained with implied open-circuit voltages（i Voc）of 715m V and saturated dark current（J₀）of 18 f A/cm².The optical band gap of poly-Si Cx was widened with increase in R,and got up to 2.3e V when R was 0.4.A proof-of-concept top/rear TOPCon solar cells,featuring a N⁺-poly-Si Cx（R=0.2）front contact,was fabricated to demonstrate the potential of this Si Cx passivation contact.While maintaining the open-circuit voltages,the short circuit current density increased by nearly 1.5 m A/cm²due to the decrease in the parasitic absorption of light at the front side.And finally,the conversion efficiency increased from 19.07%to 20.17%.The results show that the TOPCon structure based on wide band-gap silicon carbide thin film can not only obtain higher open circuit voltage,but also help to reduce optical loss and improve short-circuit current density and improve the conversion efficiency of the cell.Furthermore,replacing the homogeneous emission junction of the TOPCon solar cell with the TOPCon heterojunction of the wide band-gap will help improve the open circuit voltage of the TOPCon solar cell,which is of great significance to further improve the conversion efficiency of the TOPCon solar cell in the future.