In this work we present the preparation of highly luminescent anisotropic CdTe/CdSe colloidal heteronanocrystals. The reaction conditions used (low temperature, slow precursor addition, and surfactant composition) resulted in a tunable shape from prolate to branched CdTe/CdSe nanocrystals. Upon CdSe shell growth the heteronanocrystals show a gradual evolution from type-I to type-II optical behavior. These heteronanocrystals show a remarkably high photoluminescence quantum yield (up to 82%) and negligible thermally induced quenching up to temperatures as high as 373 K.

We present a numerical model for calculating current-voltage characteristics of polymer:fullerene bulk hetrojunction solar cells at different degrees of nanoscale phase separation. We show that the short-circuit current enhancement with finer phase separation is due to a reduction in bimolecular recombination caused by lateral movement of photogenerated electrons to the fullerene-rich phase. At high bias, vertical electron transport is enhanced and lateral movement is reduced, causing a significant field-dependent carrier extraction for coarse morphologies.

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