Efficiency enhancement of copper contaminated radial p–n junction solar cells

Radial p–n junction solar cells have been predicted theoretically to have better efficiencies than their planar counterparts due to a decrease in the distance required to collect minority carriers relative to carrier diffusion length. This advantage is also significantly enhanced when the diffusion length is much smaller than the absorption length. The radial p–n junctions studied here consist of micron-scale to nano-scale diameter holes etched into a copper contaminated silicon wafer. Radial p–n junctions contaminated with copper impurities show roughly a twofold increase in efficiency than similarly contaminated planar p–n junction solar cells; however the enhancement is a strong function of the radial junction pitch, with maximum enhancement occurring for a pitch that is twice the carrier diffusion length.