Photoconductivity from PbS-nanocrystal∕semiconducting polymer composites for solution-processible, quantum-size tunableinfrared photodetectors

We report photoconductivity at infrared wavelengths, 975–1300nm, from a polymer∕nanocrystal quantum dot composite. Biased films of the conjugated polymer poly[2-methoxy-5-(2′-ethylhexyloxy-p-phenylenevinylene)] (MEH-PPV) sensitized with PbSnanocrystals (∼5nm diameter) demonstrate photocurrent at wavelengths beyond the response of the polymer and corresponding to the absorption of the nanocrystals. The photocurrent is attributed to absorption in the nanocrystals with subsequent hole transfer to the polymer and had an internal quantum efficiency of ∼5×10−6to∼10−5charges/photon at 5V bias