Structure Design And HWCVD Preparation Of IP Composite Amorphous Silicon Film For HAC Solar Cell

Amorphous silicon/crystalline silicon heterojunction（HAC）solar cells have become the focus of current research because of their advantages of high photoelectric conversion efficiency,simple process,good repeatability and low cost.Hot wire chemical vapor deposition（HWCVD）has the advantages of no potential,no plasma bombardment,radiative divergence of the generated groups,easy process control and low cost.Currently,there are few studies on the properties of IP（I layer as intrinsic passivation layer and P layer as emitter）composite amorphous silicon film in HAC solar cells prepared by HWCVD method.In order to grasp the direction of the preparation technology of HAC solar cells and study the relationship between the thin film microstructure and the cell performance,the structure design of IP composite amorphous silicon film layer and the preparation process of HWCVD were studied in this paper,and the effect of the thin film microstructure of intrinsic passivation film layer and P-type composite emitter layer on the photoelectric performance of the cell was analyzed.The main results are as follows:1.When the intrinsic composite film layer adopts a two-layer structure design,the first layer is used as an ultra-thin passivation layer to passivate the hanging bonds on the surface of the silicon wafer more effectively,while the second layer mainly provides hydrogen atoms as a buffer layer between the intrinsic layer and the doping layer film,effectively passivating the interface layer and improving the photoelectric conversion efficiency of the HAC solar cell.The optimal thickness of the bilayer films is～0.46 nm and～6.57 nm,respectively,and the highest efficiency is22.73%.The effect of CO₂gas flow rate on the performance of HAC solar cell was studied.The results show that increasing CO₂gas flow rate according to flow gradient can improve the minority cell life and spectral response of HAC solar cell during the preparation of the first film.When CO₂/SiH₄=0.2,the minimum current loss of IP surface in HAC solar cell is 8.11 m A/cm².When the structure of the inherent composite membrane is designed as three layers,CO₂gas is injected into the first and second layers of the film,and the gas flow rate is 2.4 sccm,the short-circuit current density increases,and the efficiency of the HAC solar cell increases by 0.3%.2.The influences of the preparation parameters of intrinsic composite film such as deposition temperature,hydrogen treatment and hot wire current on the photoelectric conversion efficiency of HAC solar cells were studied.The results show that the thickness of the first layer and the second layer of the double layer intrinsic composite film is～0.57 nm and～4.54 nm,respectively.When the deposition temperature is 250℃,the minimum microstructure factor R is 0.54 and the active group of SiH bond is the most.The intrinsic composite film has the best quality,the strongest carrier transport capacity,and the highest cell efficiency is 23.45%.The thickness of the first,second and third layers is～0.31 nm,～1.39 nm and～4.93 nm,respectively,and the passivation of the silicon wafer with hydrogen for 40 s.The maximum lifetime of the cell is 5648μs,the maximum output power is 5.72 W,and the cell efficiency is 23.43%.3.P type emitter（P-type doped amorphous silicon thin film）using double light/heavy doping layer structure design,with the passivation layer and TCO layer to form a better interface contact,form PN junction at the same time,the optimization of preparation technology parameters such as substrate temperature,hydrogen treatment,current of the wire,etc,obtained the good performance of P-type layer and solar cells.The results show that the maximum photoelectric conversion efficiency(E_ff)is23.91%when the thickness of the thin film is～2.27 nm and the deposition temperature is 260℃.When the optimal hydrogen treatment time of the intrinsic composite amorphous silicon film is 80 s,the proportion of SiH bond active groups is high,the passivation performance is the best,the minority carrier lifetime is 5075μs,the thickness of the deposited P-type emitter is～2 nm and～2.39 nm,respectively,and the cell efficiency is 22.49%.When the hot wire current is 30 A and the thin film thickness is～1.86 nm and～2.23 nm,the photoelectric conversion efficiency is 22%and the filling factor is 77.37%,respectively.4.Process parameters were integrated and optimized to obtain the optimal IP structure design,that is,the intrinsic composite film layer was designed with three layers,and the P-type emitter was designed with double layers of shallow/heavy doping layer.Finally,the research group prepared a HAC solar cell with an area of156.75×156.75 mm²,and its photoelectric conversion efficiency E_ffwas 24.61%(V_ocwas 743.3 m V,FF:83.91%,J_sc:39.46 m A/cm²).