  The energetic landscape of charge transfer (CT) states at the interface of
electron donating and electron accepting domains in organic optoelectronic
devices is crucial for their performance. Central questions -- such as the role
of static energetic disorder and vibrational effects -- are under ongoing
dispute. This study provides an in-depth analysis of temperature dependent
broadening of the spectroscopic absorption and emission features of CT states
in devices with small molecule-fullerene blends. We confirm the validity of the
electro-optical reciprocity relation between the photovoltaic external quantum
efficiency ($\mathrm{EQE_{PV}}$) and electroluminescence ($\mathrm{EQE_{EL}}$),
enabling us to validate the device temperature during the experiment. The
validated temperature allows us to fit our experimental data with several
models, and compare extracted CT state energies with the corresponding open
circuit voltage limit at $0\mathrm{\,K}$. Our findings unveil that the
absorption and emission characteristics are usually not symmetric, and
dominated by temperature-activated broadening (vibrational) effects instead of
static disorder.
