Abstract
Carrier recombination at the metal contacts is a major obstacle in the development of high-performance crystalline silicon homojunction solar cells. To address this issue, we insert thin intrinsic hydrogenated amorphous silicon [a-Si: H(i)] passivating films between the dopant-diffused silicon surface and aluminum contacts. We find that with increasing a-Si: H(i) interlayer thickness (from 0 to 16nm) the recombination loss at metal-contacted phosphorus (n(+)) and boron (p(+)) diffused surfaces decreases by factors of similar to 25 and similar to 10, respectively. Conversely, the contact resistivity increases in both cases before saturating to still acceptable values of similar to 50 m Omega cm(2) for n(+) and similar to 100 m Omega cm(2) for p(+) surfaces. Carrier transport towards the contacts likely occurs by a combination of carrier tunneling and aluminum spiking through the a-Si: H(i) layer, as supported by scanning transmission electron microscopy-energy dispersive x-ray maps. We explain the superior contact selectivity obtained on n(+) surfaces by more favorable band offsets and capture cross section ratios of recombination centers at the c-Si/a-Si: H(i) interface. (C) 2014 AIP Publishing LLC.