Solution-Processed Organic Optical Upconversion Device

Area of Science:

• Optoelectronics
• Materials Science
• Photonics

Background:

• Near-infrared (NIR) imaging is crucial for machine vision and medical applications.
• NIR-to-visible optical upconverters are needed to capture NIR images with conventional cameras.

Purpose of the Study:

• To develop and characterize novel five-layer organic solution-processed upconverters (OUCs).
• To investigate both organic light-emitting diode (OLED) and light-emitting electrochemical cell (LEC) based OUCs for NIR-to-visible light conversion.

Main Methods:

• Fabrication of five-layer OUCs using a squaraine dye NIR photodetector and a super yellow polymer-based OLED or LEC.
• Characterization of device performance, including turn-on voltage and NIR-to-visible photon conversion efficiency.
• Detailed analysis of the temporal dynamics and ionic behavior of the LEC-OUC.

Main Results:

• Both OLED-OUCs and LEC-OUCs successfully converted 980 nm NIR light to yellow light (~575 nm).
• Achieved comparable device performance with a turn-on voltage of 2.7-2.9 V and ~1.6% photon conversion efficiency.
• Demonstrated that the ionic distribution in LEC-OUCs can be "frozen" by applying a small voltage, creating a stable state for measurements.

Conclusions:

• Solution-processed OUCs offer a viable method for NIR-to-visible light conversion.
• LEC-OUCs exhibit unique temporal dynamics that can be controlled and stabilized for quantitative measurements.
• These OUCs hold promise for advancing NIR imaging technologies.