# Circularly Polarized Long‐Persistent and Photostimulated Luminescence Enabled through Förster Resonance Energy Transfer and Upconversion Strategies

## TL;DR

This paper introduces new methods to create long-lasting circularly polarized light in organic materials, enabling potential uses in secure data storage and advanced optical devices.

## Contribution

The first demonstration of circularly polarized photostimulated luminescence in purely organic systems using FRET and upconversion strategies.

## Key findings

- CP-LPL was achieved using chiral emitters with FRET and upconversion strategies.
- Near-infrared stimulation enabled CP-PSL in the FRET-based system.
- Mirror-image CPL signals were observed in both design approaches.

## Abstract

Circularly polarized luminescence (CPL) has attracted significant attention for applications in displays, data encryption, anti‐counterfeiting, and bioimaging. However, extending the emission lifetime beyond the second timescale remains a challenge. Here, we report circularly polarized long‐persistent luminescence (CP‐LPL) and the first evidence of circularly polarized photostimulated luminescence (CP‐PSL) in purely organic systems. Using the chiral emitter R/S‐OBN‐Cz, we establish two complementary design strategies: (i) a three‐component Förster resonance energy transfer (FRET) system, where the energy of long‐lived charge‐separated states between the donor and the acceptor is transferred to the chiral dopant, and (ii) a two‐component upconversion system, where the locally excited state of chiral emitter is restored upon charge recombination. Both approaches result in CP‐LPL with mirror‐image CPL signals. Moreover, in the three‐component FRET system, trapped charges in the chiral dopant can be released upon near‐infrared stimulation, regenerating circularly polarized emission. This work establishes new proof of concept in chiroptical materials research, paving the way toward the practical applications in encrypted optical storage and advanced photonic devices.

Using chiral emitters with circularly polarized luminescence (CPL) characteristics integrated into organic long‐persistent luminescence (OLPL) system demonstrates circularly polarized long‐persistent luminescence (CP‐LPL). Importantly, the Förster resonance energy transfer (FRET)‐based design reveals circularly polarized photostimulated luminescence (CP‐PSL) upon near‐infrared stimulation for the first time.