Spontaneous exciton dissociation enables spin state interconversion in delayed fluorescence organic semiconductors.

ABSTRACT: Engineering a low singlet-triplet energy gap (ΔE_ST) is necessary for efficient reverse intersystem crossing (rISC) in delayed fluorescence (DF) organic semiconductors but results in a small radiative rate that limits performance in LEDs. Here, we study a model DF material, BF2, that exhibits a strong optical absorption (absorption coefficient = 3.8 × 10⁵cm^-1) and a relatively large ΔE_ST of 0.2 eV. In isolated BF2 molecules, intramolecular rISC is slow (delayed lifetime = 260 μs), but in aggregated films, BF2 generates intermolecular charge transfer (inter-CT) states on picosecond timescales. In contrast to the microsecond intramolecular rISC that is promoted by spin-orbit interactions in most isolated DF molecules, photoluminescence-detected mag

SUBMITTER: Gillett AJ 

PROVIDER: S-EPMC8599618 | biostudies-literature | 2021 Nov

REPOSITORIES: biostudies-literature