  Exciton diffusion in organic films is crucial phenomenon in optoelectronic
devices such as organic light-emitting diodes and organic photovoltaics.
However, diffusion of exciplexes has not been actively studied despite their
ever-growing importance in such devices due to the lack of apparent
charge-transfer absorption, resulting in the absence of energy transfer (ET) to
exciplex-forming pairs. Here, the ET from exciplexes to exciplex-forming pairs
is reported by analysis of transient photo-luminescent profiles. Recent reports
and our own observation of the sub-bandgap charge-transfer absorption in
exciplex-forming systems support the ET from exciplexes to exciplex-forming
pairs. The ET mechanism is discussed in the following paper.
