Improvement of multicrystalline silicon wafer solar cells by post-fabrication wet-chemical etching in phosphoric acid

In this study, we have improved electrical characteristics such as the efficiency (η) and the fill factor (FF) of finished multicrystalline silicon (mc-Si) solar cells by using a new chemical treatment with a hot phosphoric (H₃PO₄) acidic solution. These mc-Si solar cells were made by a standard industrial process with screen-printed contacts and a silicon nitride (SiN) antireflection coating. We have deposited SiN thin layer (80 nm) on p-type mc-Si substrate by the mean of plasma enhanced chemical vapour deposition (PECVD) technique. The reactive gases used as precursors inside PECVD chamber are a mixture of silane (SiH₄) and ammonia (NH₃) at a temperature of 380°C. The developed H₃PO₄ chemical surface treatment has improved η from 5·4 to 7·7% and FF from 50·4 to 70·8%, this means a relative increase of up to 40% from the initial values of η and FF. In order to explain these improvements, physical (AFM, EDX), chemical (FTIR) and optical (spectrophotometer) analyses were done.