  Charges in conjugated polymer materials have a strong impact on the
photophysics and their interaction with the primary excited state species has
to be taken into account in understanding device properties. Here, we employ
single-molecule spectroscopy to unravel the influence of charges on several
photoluminescence (PL) observables. The charges are injected either
stochastically by a photochemical process, or deterministically in a
hole-injection sandwich device configuration. We find that upon charge
injection, besides a blue-shift of the PL emission and a shortening of the PL
lifetime due to quenching and blocking of the lowest-energy chromophores, the
non-classical photon arrival time distribution of the multichromophoric chain
is modified towards a more classical distribution. Surprisingly, the fidelity
of photon antibunching deteriorates upon charging, whereas one would actually
expect the number of chromophores to be reduced. A qualitative model is
presented to explain the observed PL changes. The results are of interest to
developing a microscopic understanding of the intrinsic charge-exciton
quenching interaction in devices.
