Progress in the development of all-back-contacted silicon solar cells

N-type all-back-contact (ABC) silicon solar cells incorporating a simple oxide-nitride passivation scheme are presently being developed at the Australian National University. Having already achieved promising efficiencies with planar ABC cells [1], this work analyses the cell performance after integrating a surface texturing step into the process flow. Although the textured cells have significantly lower front surface reflection, the measured short-circuit current density is actually lower than that of the planar cells. Photoconductance decay data indicate the presence of high carrier recombination at the textured surface of the ABC cells, which are deposited with a stack of thermal oxide and LPCVD nitride. Further examination confirmed that high carrier recombination is due to stress induced by the LPCVD nitride on the peaks and valleys of the textured surface. Use of PECVD nitride instead of LPCVD nitride as an antireflection layer avoids the degraded carrier lifetime caused by the textured surface. Therefore, PECVD nitride should be a good substitute for constructing the oxide-nitride stacks of our future ABC cells.