Multi-Crystalline Silicon Based Heterojunction Solar Cells

Abstract

Heterojunction solar cells are fabricated on 1 Ωcm boron or phosphorus doped multicrystalline silicon wafers. As-cut material is treated by industrial isotexturing and home-made acidic texturing in order to obtain textured surfaces, as well as CP4 and modified CP6 chemical polishing, in order to obtain reference samples. A double a-Si:H/c-Si is deposited by Plasma Enhanced Chemical Vapour Deposition to sandwich the substrate, at the sunward surface to form the emitter and at the rear side to act as back surface field. High open-circuit current (625 mV) is obtained on flat p-type mc-Si, whereas commercial acidic surface treatment, commonly used in diffused junction mc-Si solar cell fabrication, requires a level of passivation which is not easily achievable using the very thin a-Si:H film needed in heterojunction technology. On n-type substrates, conversion efficiency around 12% is found, despite low VOC values. The effectiveness of a-Si:H/mc-Si technology in achieving high photovoltaic efficiency using low thermal budget manufacturing process is demonstrated.