Achievement

IGERT Fellow Joshua Choi and his collaborators studied quantum tunneling between lead chalcogenide nanocrystals. By attaching various molecules to the nanocrystal surface, they were able to finely tune the distance between the nanocrystals. They showed for the first time that, when the nanocrystals are close enough to each other, quantum interactions split electron-hole pairs generated by light absorption. This finding has important implications for nanocrystal-based solar cell designs. They fabricated solar cells using this splitting mechanism and achieved 3.6% efficiency -- the highest efficiency to data for lead chalcogenide nanocrystals. These nanocrystals are promising candidates for next-generation solar cells due to their low cost and potentially high efficiency. Compared to conventional (silicon) solar cells, which have good efficiency but extremely high cost, nanocrystal-based devices should be economically viable for widespread deployment even at moderate efficiencies (~10%).