The team has demonstrated that a SiO2/SiNx stack can provide a good passivation effect on electrical properties upon heavily doped SiNWs, reducing both the Shockley-Read-Hall recombination and near surface Auger recombination, while maintaining the excellent anti-reflection and light-trapping effects of these structures.

"We have degraded the recombination rate at and near the surface to 20% in SiO2/SiNx stack passivated SiNW based solar cells compared with bare SiNW cells,” X X Lin told nanotechweb.org.

What’s more, the efficiency of the SiNW based solar cells can be further improved with a carefully designed diffusion process, in order to minimize the unfavorable Auger recombination near the surface.

"The sheet resistance of our samples after diffusion is around 75 Ω/sq," commented X Hua. "In the next stage of our work we would like to increase the sheet resistance to higher than 125–150 Ω/sq."

W Z Shen, who leads the team, explains that the group is improving the cell performance by introducing a selective emitter structure and selective growth of SiNWs in the active area for better front electrical contact.

Full details can be found in the journal Nanotechnology.