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

## TL;DR

This paper presents a dye-sensitized CdSe nanocrystal optical transistor with a high ON/OFF ratio and fast 74 ns rise time, enabled by rapid electron transfer from dye to nanocrystals, suitable for telecom applications.

## Contribution

It introduces a novel dye-sensitized nanocrystal transistor demonstrating high ON/OFF ratio and fast optical gating in the telecom window, with detailed insights into charge transfer mechanisms.

## Key findings

- High ON/OFF ratio of six orders of magnitude in the red spectral region.
- Fast 74 ns rise time achieved for near-infrared optical gating.
- Electron transfer from dye to CdSe nanocrystals occurs within 5 ps.

## 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.

---
Source: https://tomesphere.com/paper/1904.04752