We integrate the electro-attractive conjugated molecule tetrafluoro-tetracyano-quinodimethane (F4TCNQ) in the active layer of polymer-CdSe colloidal quantum dot (cQD) solar cells. The addition of this molecule enhances cQD dispersion inside the polymer. In tuning its concentration, we can optimize the active layer morphology for charge separation and transport. A smoother morphology is likely the result of polymer chain adsorption on cQDs via F4TCNQ which increases the steric barrier between cQDs. Our most optimized device has a F4TCNQ:cQDs weight ratio of 0.5% improving the power conversion efficiency by a factor ∼2.3.

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ZnxCd1-xS alloyed shells and Mn2+ ions were studied as means to confine charge carriers away from the surface of nanocrystals. In the former case, the electron confinement potential increased with the Zn fraction in CdSe/ZnxCd1-xS colloidal quantum dots and their photoluminescence blueshifted by ~50 nm. However, structural defects and polydispersity became important in samples with x >0.7 likely due to a phase transition and to strain increasing with core/shell lattice mismatch reaching 12% when x = 1. In the latter case, the Mn2+ ions diffused within MnyZn1-ySe/ZnSe nanocrystals act as localized luminescent centers and their density can be controlled with the Mn fraction in the alloyed core. The ions are excited through energy transfers from excitons in the ZnSe, and given the long lifetime of the Mn2+ first excited state, thermoactivated reverse energy transfer also occurred and emission from the ZnSe excitons was observed.