  The electronic structures of boron nitride nanotubes (BNNTs) doped by
different organic molecules under a transverse electric field were investigated
via first-principles calculations. The external field reduces the energy gap of
BNNT, thus makes the molecular bands closer to the BNNT band edges and enhances
the charge transfers between BNNT and molecules. The effects of the electric
field direction on the band structure are negligible. The electric field
shielding effect of BNNT to the inside organic molecules is discussed. Organic
molecule doping strongly modifies the optical property of BNNT, and the
absorption edge is red-shifted under static transverse electric field.
