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Comment on Frequency response and origin of the spin-1/2 photolumines-cence-detected magnetic resonance in a pi-conjugated polymer

C. G. Yang·E. Ehrenfreund·Z. V. Vardeny
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Abstract

In a recent paper Segal et al. [1] attempted to explain the dynamics of spin 1/2 photoluminescence detected magnetic resonance (PLDMR) in films of a pi-conjugated polymer, namely a soluble de-rivative of poly(phenylene-vinylene) [MEH-PPV] using a model (dubbed TPQ), in which the PLDMR is due to spin dependent triplet-polaron interactions that reduce the polarons density and consequent quenching of singlet excitons. We studied the full PLDMR and photoinduced ab-sorption (PA) dynamics of MEH-PPV films as a function of microwave power at various tempera-tures. We show, firstly, that the TPQ model is incompatible with the full frequency dependent spin 1/2 PLDMR response; secondly, it is not in agreement with the spin-1 PLDMR temperature dependence; thirdly, it predicts a much shorter triplet exciton lifetime than that obtained experimentally; and fourthly, that is in contradiction with the temperature dependencies of spin 1/2 PLDMR and triplet exciton PA. In contrast, an alternative model, namely the spin dependent re-combination of polarons, is capable of explaining the whole body of experimental results, and in particular the PLDMR dynamics.

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C. G. Yang, E. Ehrenfreund, Z. V. Vardeny. 2006-05-12. Comment on Frequency response and origin of the spin-1/2 photolumines-cence-detected magnetic resonance in a pi-conjugated polymer. https://doi.org/10.1103/physrevb.75.246201

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