Triplet Excitons Quenching By Doublet Centers in a Nanoreactor with an External Magnetic Field

The process of spin-selective quenching of a triplet (T) exciton by a fixed spin doublet (D) center in an organic semiconductor nanoparticle (anthracene, tetracene, MEH–PPV) was studied. Random walks of the T-exciton in a spherical nanovolume of a crystal or polymer globule were modeled based on the solution of the Neumann boundary diffusion condition. Time dependences of the spin-nonselective quenching rate of T-excitations were calculated for different values of geometric and diffusion parameters. Taking into account the spin dynamics of T–D-pair reagents allowed calculating magnetic field effects of T–D-quenching rate, which showed a strong influence of the nanoparticles size and initial position of the T-exciton and doublet sink on the absolute value of the effect. The obtained radial dependences of the magnetic field modulation of the quenching efficiency can be approximated by a superposition of two exponents.