We demonstrate that semiconductor nanorods can be used to fabricate readily processed and efficient hybrid solar cells together with polymers. By controlling nanorod length, we can change the distance on which electrons are transported directly through the thin film device. Tuning the band gap by altering the nanorod radius enabled us to optimize the overlap between the absorption spectrum of the cell and the solar emission spectrum. A photovoltaic device consisting of 7-nanometer by 60-nanometer CdSe nanorods and the conjugated polymer poly-3(hexylthiophene) was assembled from solution with an external quantum efficiency of over 54% and a monochromatic power conversion efficiency of 6.9% under 0.1 milliwatt per square centimeter illumination at 515 nanometers. Under Air Mass (A.M.) 1.5 Global solar conditions, we obtained a power conversion efficiency of 1.7%.

We have shown recently that the use of high aspect ratio inorganic nanorods in conjunction with conjugated polymers is a route to obtaining efficient solar cells processed from solution. Here, we demonstrate that the use of binary solvent mixtures in which one of the components is a ligand for the nanocrystals is effective in controlling the dispersion of nanocrystals in a polymer.By varying the concentration of the solvent mixture, phase separation between the nanocrystal and polymer could be tuned from a micron scale down to nanometer scale. In addition, we can achieve nanocrystal surfaces that are free of surfactant through the use of weak binding ligands, which can be removed through heating. Combined, the control of film morphology together with surfactant removal result in nanorod-polymer blend photovoltaic cells with high external quantum efficiency of 59% under 0.1 mW/cm 2 illumination at 450 nm.

Charge separation and charge transport have been limiting factors in photovoltaic cells that utilize conjugated polymer blends. These authors have exploited the ability of a soluble perylene dye (see Figure) to form crystals within a polymer matrix to achieve a blend that enables good charge transfer and separation, due largely to the crystals' ability to act as electron traps.

Charge transport in composites of inorganic nanorods and a conjugated polymer is investigated using a photovoltaic device structure. We show that t he current-voltage (I-V) curves in the dark can be modelled using the Shockley equation modified to include series and shunt resistance at low current levels, and using an improved model that incorporates both the Shockley equation and the presence of a space charge limited region at high currents. Under illumination the efficiency of photocurrent generation is found to be dependent on applied bias.Furthermore, the photocurrent-light intensity dependence was found to be sublinear. An analysis of the shunt resistance as a function of light intensity suggests that the photocurrent as well as the fill factor is diminished as a result of increased photoconductivity of the active layer at high light intensity. By studying the intensity dependence of the open circuit voltage for nanocrystals with different diameters and thus band gaps, it was inferred that Fermi-level pinning occurs at the interface between the aluminum electrode and the nanocrystal.3