Transport and Phototransport in ITO Nanocrystals with Short to Long-Wave Infrared Absorption

TL;DR

This study explores the infrared photoconductive properties of tin-doped indium oxide (ITO) nanocrystals, demonstrating tunable plasmonic absorption and bolometric photoresponse, offering a non-toxic alternative for infrared optoelectronic devices.

Contribution

It provides new insights into the infrared absorption and photoconductive behavior of ITO nanocrystals, highlighting their potential for low-cost, tunable infrared optoelectronics.

Findings

In2O3 nanoparticles exhibit intraband absorption in the mid-infrared range.

Doping induces plasmonic features with a cross section of 1-3x10^-13 cm^2.

Nanocrystals become conductive and photoconductive through ligand exchange, showing a bolometric response.

Abstract

Nanocrystals are often described as an interesting strategy for the design of low-cost optoelectronic devices especially in the infrared range. However the driving materials reaching infrared absorption are generally heavy metalcontaining (Pb and Hg) with a high toxicity. An alternative strategy to achieve infrared transition is the use of doped semiconductors presenting intraband or plasmonic transition in the short, mid and long-wave infrared. This strategy may offer more flexibility regarding the range of possible candidate materials. In particular, significant progresses have been achieved for the synthesis of doped oxides and for the control of their doping magnitude. Among them, tin doped indium oxide (ITO) is the one providing the broadest spectral tunability. Here we test the potential of such ITO nanoparticles for photoconduction in the infrared. We demonstrate that In2O3 nanoparticles presents an intraband absorption in the mid infrared range which is transformed into a plasmonic feature as doping is introduced. We have determined the cross section associated with the plasmonic transition to be in the 1-3x10-13 cm2 range. We have observed that the nanocrystals can be made conductive and photoconductive due to a ligand exchange using a short carboxylic acid, leading to a dark conduction with n-type character. We bring further evidence that the observed photoresponse in the infrared is the result of a bolometric effect.