ANALYSIS OF O_2 CONTENT IN FRONT ITO LAYERS FOR A-SI:H/C-SI HETEROJUNCTION SOLAR CELLS

摘要

In heterojunction devices, the ITO front layer is used as an antireflection coating in order to reduce the large reflectance losses due to the high refractive index of silicon, but also it has to assure a good carrier collection, though the very thin a-Si:H emitter layer exhibits a large sheet resistance. Moreover, it can play also an important role on the passivation because of the band-bending provoked by its work function. In this work, we have processed some heterojunction solar cells with different optimized ITO layers varying the oxygen flow to see the impact on the final solar cells parameters. We have observed that when increasing the transparency of our layers, an expected gain in Jsc is observed (＞4 mA/cm~2). By contrast, a decrease of the FF due to a higher sheet resistance is also observed, clearly indicating the best compromise for our device in terms of global efficiency. 19% efficiency HJ solar cells on (n) c-Si substrate were fabricated on 148 cm~2 with an industrial process.