We quantify experimentally the efficiency of excitation transfer from a semiconducting polymer matrix to quantum dot nanocrystals. We study 5Ϯ0.5 nm PbS nanocrystals embedded in MEH-PPV ͑poly͓2-methoxy-5-͑2Ј-ethylhexyloxy-p-phenylenevinylene͔͒͒ polymer. We determine the excitation transfer efficiency from normalized photoluminescence excitation measurements. When the composites are made using as-synthesized PbS nanocrystals capped by oleate ligands, the excitation transfer efficiency is about 20%. Replacing these ligands with shorter chains results in a factor-of-3 enhancement in the excitation transfer efficiency. Our findings provide guidance to the realization of efficient electroluminescent devices.

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