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arXiv · 1904.04752

A Dye-Sensitized CdSe Nanocrystal Optical Transistor with High ON/OFF Ratio in the First Telecom Window with 74 ns Rise Time

Krishan Kumar·Quan Liu·Jonas Hiller·Christine Schedel·Alfred Meixner·Kai Braun·Jannika Lauth·Marcus Scheele
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Abstract

We report an optically gated transistor composed of CdSe nanocrystals (NCs), sensitized with the dye Zinc beta-tetraaminophthalocyanine for operation in the first telecom window. This device shows a high ON/OFF ratio of six orders of magnitude in the red spectral region and an unprecedented 4.5 orders of magnitude at 847 nm. By transient absorption spectroscopy, we reveal that this unexpected infrared sensitivity is due to electron transfer from the dye to the CdSe NCs within 5 ps. We show by time-resolved photocurrent measurements that this enables fast rise times during near-infrared optical gating of 74 ns. Electronic coupling and accelerated non-radiative recombination of charge carriers at the interface between the dye and the CdSe NCs are further corroborated by steady-state and time-resolved photoluminescence measurements. Field-effect transistor measurements indicate that the increase in photocurrent upon laser illumination is mainly due to the increase in carrier concentration while the mobility remains unchanged. Our results illustrate that organic dyes as ligands for NCs invoke new optoelectronic functionalities, such as fast optical gating at sub-bandgap optical excitation energies.

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Krishan Kumar, Quan Liu, Jonas Hiller, Christine Schedel, Alfred Meixner, Kai Braun, Jannika Lauth, Marcus Scheele. 2019-04-09. A Dye-Sensitized CdSe Nanocrystal Optical Transistor with High ON/OFF Ratio in the First Telecom Window with 74 ns Rise Time. https://arxiv.org/abs/1904.04752

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