Abstract
The effect of the phosphine (PH3) flow rate on the doping profile, in particular the peak doping concentration of the n(+) emitter layer, of solid phase crystallised polycrystalline silicon thin-film solar cells on glass is investigated by electrochemical capacitance-voltage profiling. The peak n(+) layer doping is found to increase with increasing PH3 gas flow, resulting in a shift of the p-n junction location towards the centre of the diode. The impact of the PH3 flow rate on the crystal quality of the poly-Si films is analysed using ultraviolet (UV) reflectance and UV/visible Raman spectroscopy. The impact of the PH3 flow rate on the efficiency of poly-Si thin-film solar cells is investigated using electrical measurements. An improvement in the efficiency by 46% and a pseudo energy conversion efficiency of 5% was obtained through precise control of the flow rate at an intermediate n(+) emitter layer doping concentration of 1.0 x 10(19) cm(-3). The best fabricated poly-Si thin-film solar cell is also found to have the highest crystal quality factor, based on both Raman and UV reflectance measurements. (C) 2013 AIP Publishing LLC.