Surface Passivation of ITO on Heterojunction Solar Cells with Enhanced Cell Performance and Module Reliability

Abstract

The indium tin oxide (ITO) thin film plays an important role in the silicon heterojunction (SHJ) solar cells, which acts as not only a carrier transport layer in vertical and lateral directions but an anti-reflection layer as well. Thickness reduction of the expensive ITO is an efficient strategy to reduce the cost of SHJ solar cells. In this work, the simulated antireflection effects of several dielectric capping layers demonstrate that Al2O3 and SiO2 are the suitable candidates for both of the SHJ solar cell and module. Hall effect measurements show that the SiO2 layer is able to passivate the ITO surface and improve the mobility and conductivity of the ITO film, which is beneficial to further reduce the thickness of ITO films. It is also found that the SiO2 capping layer can significantly enhance the adhesion strength between the solar cell and the encapsulating polymer film by 26% in the SHJ module. The improved adhesion strength is attributed to the higher surface energy of SiO2 than ITO, according to the liquid-solid contact angle measurements. These results show that the SiO2 capping layer can not only reduce the consumption of ITO thin films, but also increase the reliability of SHJ module.