Accurate wavelength tracking by exciton spin mixing

TL;DR

This paper introduces a lightweight, single-pixel wavelength tracking device using room-temperature phosphorescence, capable of nanometer resolution, suitable for simple wavelength measurements without bulky spectrometers.

Contribution

The authors develop a novel organic thin-film sensor that leverages exciton spin mixing for high-resolution wavelength tracking, replacing traditional spectrometers.

Findings

Achieves wavelength resolution down to one nanometer.

Demonstrates successful replacement of full spectrometers in applications.

Uses a solution-processed organic phosphor-quantum dot system.

Abstract

Wavelength discriminating systems typically consist of heavy benchtop-based instruments, comprising diffractive optics, moving parts, and adjacent detectors. For simple wavelengths measurements, such as lab-on-chip light source calibration or laser wavelength tracking, which do not require polychromatic analysis and cannot handle bulky spectroscopy instruments, light-weight, easy-to-process, and flexible single-pixel devices are attracting increasing attention. Here, we propose a device for wavelength tracking with room-temperature phosphorescence at the heart of its functionality that demonstrates a resolution down to one nanometer and below. It is solution-processed from a single host-guest system comprising organic room-temperature phosphors and colloidal quantum dots. The share of excited triplet states within the photoluminescent layer is dependent on the excitation wavelength and determines the afterglow intensity of the film, which is tracked by a simple photodetector. Finally, an all-organic thin-film wavelength sensor and two applications are demonstrated where our novel measurement concept successfully replaces a full spectrometer.