Annealing effect on photovoltaic performance of hybrid P3HT/In-situ grown CdS nanocrystal solar cells

The CdS nanocrystals with different aspect ratios (ARs) can be synthesized directly in the presence of conjugated polymer poly(3-hexylthiophene-2,5-diyl) (P3HT). The UV-vis spectra of the composite films show a blue shift of the - transition band with an increasing aspect ratio (AR) of the CdS nanocrystals, which was attributed to the destruction of the ordered structure of polymer chains as supported by PL measurements. Atomic force microscope measurements on P3HT/CdS film also demonstrate the aggregation of CdS nanocrystal in the P3HT matrix is more apparent for the CdS nanocrystals of AR 4 than that of AR 16, indicating a stronger interaction between P3HT and CdS for a larger AR (16), which is favorable for the network structure and formation of percolation paths to increase the transport properties of the P3HT/CdS solar cells. Therefore, a higher power conversion efficiencies (PCE) up to 2.95 can be obtained for the in-situ-grown P3HT/CdS with AR 16 upon annealing treatment at 160C for 60 min.