Research On The Sputtering-Damage And Materials Of The Window Layer For HJT Solar Cell

Indium tin oxide（ITO）thin films serve as the window layer of silicon-based heterojunction solar cells（HJT）,which play the functions of photo-generated carrier collection,lateral transport,and antireflection layer.The optoelectronic properties of ITO thin films are one of the key factors affecting the output characteristics of HJT solar cells,but the inherent contradiction between the optical properties and electrical properties of ITO thin films seriously affects the conversion efficiency of HJT solar cells.In this paper,the effects of target composition,substrate temperature,oxygen content,hydrogen content,pressure,total flow parameters and annealing treatment on the photoelectric properties of ITO thin films were studied.Due to the sensitivity of the properties of a-Si:H thin films to temperature,ion bombardment and light radiation,the influence of different coating parameters of DC magnetron sputtering on the passivation effect of the a-Si:H/c-Si interface was investigated in this paper.Effects of ITO films prepared under different parameters on sputtering damage of HJT solar cells.There are the following conclusions:（1）The transmission of ITO（In₂O₃:Sn O₂=97:3wt%）in the visible light band（380nm-780nm）is significantly higher than that of ITO（In₂O₃:Sn O₂=90:10wt%）.In terms of electrical properties,when the oxygen content is less than 2%,the resistivity of the ITO films prepared by the two targets is basically the same.When the oxygen content is higher than 3%,the resistance of ITO（In₂O₃:Sn O₂=97:3wt%）rate will increase sharply.（2）In the effects of substrate temperature,oxygen content,hydrogen content,pressure,and total flow parameters on the photoelectric properties of ITO films in magnetron sputtering,when the substrate temperature is 200℃,the film has better transmittance and lower Resistivity and better film uniformity.When the oxygen content is 2%and the hydrogen content is 0%,the photoelectric properties of the film are optimal,the transmittance can reach more than 90%,and the resistivity can be reduced to 4.011×10^-4Ω·cm.When the pressure is 0.7Pa and the total flow rate is below 200sccm,the permeability and resistivity are low.Increasing the air pressure and total flow rate will cause the transmittance of the ITO film to decrease and the resistivity to increase.（3）By normalizing the difference in minority carrier lifetime before and after ITO plating,the sputtering damage at the interface between ITO and amorphous silicon is basically the same for different target compositions,substrate temperatures,and hydrogen content,and the difference in minority carrier lifetime decreases on average.The value is maintained at around 2000-3000us.When the oxygen content is too high,the high-energy negative oxygen ion will damage the amorphous silicon and increase the sputtering damage.（4）The effect of oven annealing of ITO film is better than that of hot-table annealing.With the increase of annealing temperature and annealing time,the electrical properties of ITO films gradually decrease,but the optical properties improve.