Abstract

Topological insulators (TIs) possess exciting nonlinear optical properties due to presence of metallic surface states with the Dirac fermions and are predicted as a promising material for broadspectral phodotection ranging from UV (ultraviolet) to deep IR (infrared) or terahertz range. The recent experimental reports demonstrating nonlinear optical properties are mostly carried out on non-flexible substrates and there is a huge demand for the fabrication of high performing flexible optoelectronic devices using new exotic materials due to their potential applications in wearable devices, communications, sensors, imaging etc. Here first time we integrate the thin films of TIs (Bi2Te3) with the flexible PET (polyethylene terephthalate) substrate and report the strong light absorption properties in these devices. Owing to small band gap material, evolving bulk and gapless surface state conduction, we observe high responsivity and detectivity at NIR (near infrared) wavelengths (39 A/W, 6.1 × 108 Jones for 1064 nm and 58 A/W, 6.1 × 108 Jones for 1550 nm). TIs based flexible devices show that photocurrent is linearly dependent on the incident laser power and applied bias voltage. Devices also show very fast response and decay times. Thus we believe that the superior optoelectronic properties reported here pave the way for making TIs based flexible optoelectronic devices.

Highlights

  • Topological insulators (TIs) possess exciting nonlinear optical properties due to presence of metallic surface states with the Dirac fermions and are predicted as a promising material for broadspectral phodotection ranging from UV to deep IR or terahertz range

  • It shows the presence of bismuth and telluride and the percentage was found about Bi = 40.28 and Te = 59.72 which is very close to their atomic ratio percentage 2:3

  • The appearance or colour of the film was found to be dependent on the thickness of the film which is expected because the films or nanosheets of topological insulators exhibit thickness dependent optical p­ roperties[23,43,44]

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Summary

Introduction

Topological insulators (TIs) possess exciting nonlinear optical properties due to presence of metallic surface states with the Dirac fermions and are predicted as a promising material for broadspectral phodotection ranging from UV (ultraviolet) to deep IR (infrared) or terahertz range. The recent experimental reports demonstrating nonlinear optical properties are mostly carried out on nonflexible substrates and there is a huge demand for the fabrication of high performing flexible optoelectronic devices using new exotic materials due to their potential applications in wearable devices, communications, sensors, imaging etc. Nowadays optoelectronic devices used in optical communications or infrared imaging demand high performing photodetection properties along with flexibility of the substrate. Thin films of TIs made from the nanosheets of B­ i2Se3 and ­Bi2Te3 were integrated with the plastic substrates using colloidal nanoplates ink for investigating the optoelectronic p­ roperties[41] but films were not studied for their NIR photodetector performances e.g. responsivity and detectivity. The NIR responsivity observed in these devices is in the range of 30–60 A /W which is very competitive for technological applications

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