Comment on On the Yield of Singlet Excitons in Organic Light-Emitting   Devices: a Double Modulation Photoluminescence-Detected Magnetic Resonance   Study
  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. 
C. G. Yang, E. Eherenfreund, Z. V. Vardeny