20.1% efficient large area cell on 140 micron thin silicon wafer

The laser-grooved buried contact (LGBC) crystalline silicon solar cell has a selective emitter with excellent response to the solar spectrum in the wavelength range 300-900 nm. However, the cell efficiency is limited by a reduced response in the 900-1200 nm region of the spectrum due to the high recombination characteristics of the rear aluminium back surface contact and reduced internal reflection at this interface. The LGBC cell has now been fabricated with an aluminium laser-fired contact (LFC) through a passivating rear silicon oxide dielectric. The cells were processed using FZ wafers of resistivity 0.5 ohm.cm to produce a 140 µm thin cell of 20% efficiency. The performance gain produced with the LFC process is clearly seen in the spectral response and internal reflection in the long wavelength region of the spectrum (900-1200 nm). This process offers the potential for premium efficiency, cost-competitive photovoltaic cells with a silicon feedstock consumption of less than 6 g/Wp.