Phototransport in networks of tetrapod-shaped colloidal semiconductor nanocrystalsElectronic supplementary information (ESI) available: Details on chemicals, syntheses and assembly procedures; estimate of nanocrystal concentrations, average number of surfactants bound to their surface, and ratio of number of additive molecules to bound surfactants; transport characteristics of "as-deposited" non-annealed films; additional SEMs of deposited films; TEMs of networks before and after annealing; AFM

Tetrapod-shaped CdSe(core)/CdTe(arms) colloidal nanocrystals, capped with alkylphosphonic acids or pyridine, were reacted with various small molecules (acetic acid, hydrazine and chlorosilane) which induced their tip-to-tip assembly into soluble networks. These networks were subsequently processed i...

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Main Authors: Franchini, Isabella R, Cola, Adriano, Rizzo, Aurora, Mastria, Rosanna, Persano, Anna, Krahne, Roman, Genovese, Alessandro, Falqui, Andrea, Baranov, Dmitry, Gigli, Giuseppe, Manna, Liberato
Format: Article
Language:English
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Summary:Tetrapod-shaped CdSe(core)/CdTe(arms) colloidal nanocrystals, capped with alkylphosphonic acids or pyridine, were reacted with various small molecules (acetic acid, hydrazine and chlorosilane) which induced their tip-to-tip assembly into soluble networks. These networks were subsequently processed into films by drop casting and their photoconductive properties were studied. We observed that films prepared from tetrapods coated with phosphonic acids were not photoconductive, but tip-to-tip networks of the same tetrapods exhibited appreciable photocurrents. On the other hand, films prepared from tetrapods coated with pyridine instead of phosphonic acids were already highly photoconductive even if the nanocrystals were not joined tip-to-tip. Based on the current-voltage behavior under light we infer that the tunneling between tetrapods is the dominant charge transport mechanism. In all the samples, chemically-induced assembly into networks tended to reduce the average tunneling barrier. Additionally, pyridine-coated tetrapods and the tip-to-tip networks made out of them were tested as active materials in hybrid photovoltaic devices. Overall, we introduce an approach to chemically-induced tip-to-tip assembly of tetrapods into solution processable networks and demonstrate the enhancement of electronic coupling of tetrapods by various ligand exchange procedures. We introduce an approach to chemically-induced tip-to-tip assembly of tetrapods into solution processable networks and demonstrate the enhancement of electronic coupling of tetrapods by various ligand exchange procedures.
ISSN:2040-3364
2040-3372
DOI:10.1039/c0nr00308e