# High‐Performance Flexible Near‐Infrared Organic Light‐Emitting Diodes with a Heterogeneous Alloy Semitransparent Electrode

## TL;DR

A new flexible near-infrared OLED design uses a magnesium-bismuth alloy electrode to improve light efficiency and achieve record performance.

## Contribution

A magnesium-bismuth alloy electrode is introduced to enhance efficiency in flexible near-infrared OLEDs.

## Key findings

- The Mg-Bi alloy electrode achieves 40% broadband transmittance and 29.3 Ω ◻−1 conductivity.
- The design reaches 42.3% light outcoupling efficiency and 71.8% photoluminescence quantum yield.
- Flexible NIR OLEDs achieve a record 24.3% external quantum efficiency.

## Abstract

Flexible near‐infrared (NIR) organic light‐emitting diodes (OLEDs) face efficiency challenges due to low photoluminescence quantum yields (PLQYs) in NIR emitters, governed by the energy gap law. Accelerating radiative transitions via the Purcell effect in optical microcavities offers a solution, but conventional flexible semitransparent electrodes struggle to balance microcavity‐enhanced PLQY and light outcoupling efficiency (OCE). We address this with a micro‐structured magnesium‐bismuth (Mg‐Bi) alloy electrode offering 40% broadband transmittance (400–1600 nm) and conductivity (29.3 Ω ◻−1). The alloy's low real permittivity supports less confined surface plasmon polariton and, with a capping layer, yields 60% NIR transmittance in an organic‐to‐air optical configuration. This design achieves 42.3% OCE and elevates the PLQY of a 704 nm NIR emitter to 71.8%, enabling flexible NIR‐OLEDs with a record 24.3% external quantum efficiency. The synergy of optical engineering and conductive microstructures establishes a universal strategy for high‐efficiency flexible NIR optoelectronics.

This study presents a micro‐structured magnesium‐bismuth alloy electrode that enhances flexible NIR OLEDs. The electrode provides 40% broadband transmittance (400–1600 nm) and boosts light outcoupling efficiency (42.3%) and photoluminescence quantum yield (71.8%) through the Purcell effect in optical microcavities. This design achieves a record‐breaking 24.3% external quantum efficiency for flexible NIR OLEDs.