The steady-state photoluminescence (SSPL) spectra in toluene gradually red-shift from DMACBP (lPL = 595 nm) to DMACBPN (lPL = 630 nm) and DMACPyBPN (lPL = 672 nm), which coincides with an increasing number of nitrogen atoms in the acceptors (Figure ). However, DMACPyBP (lPL = 645 nm) containing three nitrogen atoms within the acceptor exhibits a slightly red-shifted emission than DMACBPN (lPL = 630 nm), which contains four nitrogen atoms within the acceptor. This behavior correlates with the calculated S1 energies (Figure )and demonstrated that acceptor PyBP with 10-position N showed more stronger electron-withdrawing abilities than BPN acceptor with two N in [1,10] phenanthroline, following the trend of acceptor strength as shown in Figure .