Diffusion mechanism of exciplex. 2. Energy transfer mechanism

Excited-state charge-transfer complexes (exciplexes) have been actively exploited in organic optoelectronic devices to improve performance; however, diffusion of exciplexes has not been actively studied despite its influence on performance due to the lack of apparent charge-transfer absorption. In the preceding paper, we studied the energy transfer (ET) from exciplexes to exciplex-forming pairs in relation to the charge-transfer absorption of the exciplex state, resulting in the exciplex diffusion. In this paper, we report that the ET takes place dominantly via the Dexter-type exchange mechanism, from the exponential decrease of the ET rate constant with separation between exciplexes.