  We report excited state emission from p-states at excitation fluences well
below ground state saturation in CdSe nanoplatelets. Size dependent exciton
ground state-excited state energies and dynamics are determined by three
independent methods, time-resolved photoluminescence (PL), time-integrated PL
and Hartree renormalized k$\cdot$p calculations -- all in very good agreement.
The ground state-excited state energy spacing strongly increases with the
lateral platelet quantization. Our results suggest that the PL decay of CdSe
platelets is governed by an LO-phonon bottleneck, related to the reported low
exciton phonon coupling in CdSe platelets and only observable due to the very
large oscillator strength and energy spacing of both states.
