We use quasi-steady-state photoinduced absorption (PIA) to study charge generation in blends of poly(3-hexylthiophene-2,5-diyl) (P3HT) with PbS nanocrystal quantum dots as a function of excitation energy. We find that, per photon absorbed, the yield of photogenerated holes present on the conjugated polymer increases with pump energy, even at wavelengths where only the quantum dots absorb. We interpret this result as direct evidence for transfer of hot holes in these conjugated polymer/quantum dot blends. These results help understand the operation of hybrid organic/inorganic photovoltaics.
Keywords: charge transfer; exciton; photoinduced absorption spectroscopy; quantum dots; solar cell.