  We present a theoretical study of the charging effects in single and double
layer black phosphorus quantum dots (BPQDs) with lateral sizes of 2 nm and 3
nm. We demonstrate that the charging of BPQDs are able to store up to an
$N_{max}$ electron (that depends on the lateral size and number of layers in
the QD), after which structural instabilities arises. For example, 3 nm wide
hydrogen-passivated single layer BPQDs can hold a maximum of 16 electrons, and
an additional electron causes the expelling of hydrogen atoms from the QD
borders. We also calculated the additional energy ($E_A$) spectrum. For single
layer QDs with 2 and 3 nm of lateral sizes, the average $E_A$ is around 0.4 eV
and 0.3 eV, respectively. For double layer QDs with the same sizes, the average
$E_A$ is around 0.25 eV and 0.2 eV, respectively.
