  To search for high-efficiency narrow-band donor materials to improve the
short-circuit current density ($J_{sc}$) of organic solar cells, a series of
small molecules based in Bodipy-Triphenylamine were characterized using density
functional theory (DFT) and time-dependent (TD-DFT) calculations. According to
the energy of the exciton driving force they have the appropriate energy levels
to match \textbf{\textit{PC$_{61}$BM}}. The properties affecting the open
circuit voltage ($V_{oc}$), $J_{sc}$ and the fill factor ($FF$) were
investigated by calculating the geometric structures, the boundary molecular
orbital energy levels, absorption spectra, light collection efficiencies, chare
transfer rates, and exciton binding energies. The results show that the
\textbf{\textit{BTPA~III}} system has a lower LUMO level, high absorption
efficiency, and exction dissociation than other molecular systems, facilitating
the improvement of $V_{oc}$, $J_{sc}$ and $FF$. Finally,
\textbf{\textit{BTPA~III}} would be the most promising of this series of donors
and further increase the efficiency of the device.
