  In a recent Letter Lee et al. studied the spin 1/2 photoluminescence-detected
magnetic resonance (PLDMR) of a soluble derivative of poly-phenylene vinylene
[MEH-PPV] and argued that it originates from the interaction of triplet
excitons with polarons. We show that in MEH-PPV as well as in other conjugated
polymers the spin 1/2 PLDMR does not depend on the triplet exciton density and
thus cannot be associated with triplet excitons.
