# High Power, Efficient, and Stable Quantum Dot-Based Downconverters for SWIR Applications

## TL;DR

Researchers developed efficient and stable quantum dot-based devices that convert visible light to shortwave infrared, achieving high performance and cost-effectiveness.

## Contribution

A scalable route to high-performance, low-cost shortwave infrared light sources using lead sulfide quantum dots with enhanced stability and efficiency.

## Key findings

- Quantum dot downconverters achieved a record emission power density of 385 mW/cm² at 1380 nm.
- Operational stability exceeded 230 hours at 190 mW/cm² emission power density.
- Optical power conversion efficiency reached 10% using a sapphire substrate and distributed Bragg reflector.

## Abstract

Shortwave infrared light sources are indispensable for
various
applications, including advanced imaging, spectroscopy, and sensing,
yet their widespread adoption is limited by the high cost of epitaxial
semiconductors, such as InGaAs. Downconverters (DCs) offer a cost-effective
alternative, and quantum dots (QDs) stand out due to their high photoluminescence
quantum yield, size-tunable emission, and solution processability.
However, QD-DCs suffer from performance degradation under high excitation
power densities due to significant heat generation in the process
of light absorption. Here we have developed high-power, stable, and
spectrally tunable narrowband and broadband SWIR DCs (1000–1600
nm) based on Lead sulfide QDs. By mixing two different-sized QDs,
we exploit Förster resonance energy transfer and photon reabsorption
to realize a binary system with a high photoluminescence quantum yield
of 35%. Embedding the QDs in a poly­(methyl methacrylate) host mitigates
local thermal stress on the QDs, enabling standalone DCs with a high
emission power density (EmPD) of 110 mW/cm2 at 1380 nm.
Further optimization with a spectrally selective distributed Bragg
reflector for enhanced light extraction and a sapphire substrate for
efficient heat dissipation, we achieved a record EmPD of 385 mW/cm2 at 1380 nm with optical power conversion efficiency of 10%
and operational stability above 230 h at an EmPD of 190 mW/cm2. This demonstrates a scalable route to low-cost SWIR light
sources, narrowing the performance gap between solution-processed
DCs and conventional epitaxial semiconductors.