Novel Cerium-Based p-Dopants with Low Parasitic Absorption for Improved Organic Devices

Area of Science:

• Materials Science
• Organic Electronics
• Optoelectronics

Background:

• Molecular doping is crucial for high-performance organic optoelectronic devices, enabling high electrical conductivity and charge carrier injection.
• Current small molecule dopants and their charge-transfer complexes exhibit strong absorption in the visible and near-infrared (NIR) spectrum, causing performance losses in light-harvesting and light-emitting applications.
• Parasitic absorption limits the efficiency of organic optoelectronic devices, especially in applications requiring specific wavelength ranges.

Purpose of the Study:

• To introduce a new class of vacuum-processable cerium-based p-dopants.
• To address the issue of parasitic absorption in molecularly doped organic layers.
• To enhance the performance of organic optoelectronic devices, particularly NIR photodetectors, by reducing optical losses.

Main Methods:

• Synthesis and characterization of novel cerium-based p-dopants.
• Fabrication and testing of organic layers doped with new cerium-based materials.
• Incorporation of these dopants into near-infrared (NIR) narrowband organic photodetectors.
• Comparison of device performance with state-of-the-art dopants like F6-TCNNQ.
• Theoretical simulations to understand reduced polaron absorption.

Main Results:

• The novel cerium-based dopants exhibit excellent processing properties and strong doping capabilities, even in organic hole transport layers with low-lying valence levels.
• A substantial reduction in parasitic absorption was observed in layers doped with the new cerium-based materials across the visible and NIR spectrum.
• Reduced polaron absorption of the dopant anions was confirmed through theoretical simulations, aligning with experimental findings.
• Organic photodetectors incorporating these dopants showed a one-order-of-magnitude increase in specific detectivity compared to devices using F6-TCNNQ.
• Optical-microcavity-enhanced photodetectors demonstrated a significantly reduced full-width at half maximum (FWHM).

Conclusions:

• The developed cerium-based p-dopants offer a promising solution to mitigate parasitic absorption in organic optoelectronics.
• These dopants enable more efficient and wavelength-selective infrared detectors by reducing optical losses.
• The findings pave the way for improved performance in various organic optoelectronic applications, including advanced displays and sensitive photodetectors.