Highly transparent and conductive ITO substrates for near infrared applications

Rinu Abraham Maniyara,Gerasimos Konstantatos,Valerio Pruneri,Prantik Mazumder,David E Baker,Yu Bi,Bruno Paulillo,Gervasi Herranz,Christina Graham,Yu Chen

doi:10.1063/5.0040864

Abstract

Indium tin oxide (ITO) is the most widely used transparent conductor in applications such as light emitting diodes, liquid crystal devices, touch screens, and photovoltaic cells. So far, its use has mainly been limited to the visible range (380 nm–750 nm), as it reflects at longer wavelengths and, consequently, its transmission is low. Here, we introduce a simple technique, based on high temperature annealing, which can reduce reflection in the near-infrared range (750 nm–2400 nm). With an optimized set of parameters, we were able to modulate the ITO properties and achieve a high transmission, greater than 80% including substrate contribution, at telecommunication wavelengths (C-band, 1530 nm–1565 nm) while still maintaining high electrical conductivity (resistivity &lt;1.9 × 10−4 Ω cm). By using the newly developed infrared ITO transparent conductor, we demonstrate quantum dot solar cells with 27.7% enhancement in external quantum efficiency at the first exciton peak (1650 nm), and liquid crystal switching devices with 25% enhancement in transmission, with respect to device counterparts incorporating commercially available ITO.

Highlights

INTRODUCTIONTransparent conductors (TCs), which are materials capable of conducting electrical signals while transmitting light at the same time, play a critical role in many optoelectronic and photonic applications, such as liquid crystal displays, touch screens, photovoltaic cells, light emitting diodes (LEDs), smart windows, and EMI shielding
Transparent conductors (TCs), which are materials capable of conducting electrical signals while transmitting light at the same time, play a critical role in many optoelectronic and photonic applications, such as liquid crystal displays, touch screens, photovoltaic cells, light emitting diodes (LEDs), smart windows, and EMI shielding.1–6Most of the research work on TCs has focused on the visible (VIS) spectral range (380 nm–750 nm)
We demonstrate the development of Indium tin oxide (ITO)-based near-infrared transparent conductors (NIR-TCs) with low infrared reflectivity and absorption, with high optical transmission, average 78% over 750 nm–2400 nm and more than 80% at 1550 nm, including substrate contribution, while still maintaining a high electrical conductivity

Summary

INTRODUCTION

Transparent conductors (TCs), which are materials capable of conducting electrical signals while transmitting light at the same time, play a critical role in many optoelectronic and photonic applications, such as liquid crystal displays, touch screens, photovoltaic cells, light emitting diodes (LEDs), smart windows, and EMI shielding.. The proposed NIR-TCs maintain high optical transmission in the VIS (>83% over 380 nm–750 nm) This is achieved by a scalable and simple process: rapid thermal annealing with an optimized set of parameters in a controlled atmosphere. We investigated and compared the effect of high temperature annealing (HTA, greater than 700 ○C) on the properties of ITO over a broad optical spectrum. To investigate the effect of HTA time on optical properties of ITO, the as-deposited ITO films were annealed at 750 ○C for different times between 15 min and 10 h, and their corresponding optical spectra were recorded.

ITO HTA 10 h

Findings

SUMMARY