# Dynamic Behavior of Bound Interlayer Excitons in Interlayer-Doped Cs3Bi2Br9 Vacancy-Ordered Perovskite

## TL;DR

This study explores how interlayer doping with silver affects the behavior of excitons in a 2D perovskite material, revealing temperature-dependent emission patterns and potential applications in optoelectronics.

## Contribution

The paper introduces a novel understanding of bound interlayer exciton dynamics in Ag-doped Cs3Bi2Br9 using single-particle spectroscopy.

## Key findings

- Three emission regimes are observed in Ag-doped Cs3Bi2Br9 across different temperatures.
- Subpicosecond STE formation and long-lived BIE absorption are detected using ultrafast imaging.
- Homogeneous Ag doping is confirmed through spatially uniform signals.

## Abstract

Interlayer doping of the vacancy-ordered 2D perovskite
Cs3Bi2Br9 (CBB) enables the formation
of bound
interlayer excitons (BIEs), a unique charge-transfer excited state
within the layered solid. BIEs previously reported with silver (Ag+) as an interlayer dopant exhibited bright broadband photoluminescence
(PL) with prolonged lifetime at room temperature, offering potential
applications in efficient white light emission, photocatalysis, and
optoelectronics. However, the dynamic behavior of radiation and excited
carriers remains poorly understood due to the limitations of ensemble
spectroscopic measurements. Here, we investigate the temperature-dependent
dynamics of Ag-doped Cs3Bi2Br9 (Ag-CBB)
using single-particle time-resolved PL spectroscopy and ultrafast
transient absorption imaging. Single-particle PL measurements reveal
three distinct emission regimes across temperature: (i) BIE-dominant
emission at high temperatures, (ii) a mixture of radiation from BIEs
and self-trapped excitons (STEs) at intermediate temperatures, and
(iii) STE-dominant emission below 100 K. Rapid transient absorption
mapping using Parallel Rapid Imaging with Spectroscopic Mapping (PRISM)
reveals subpicosecond STE formation in pristine CBB and long-lived
photoinduced absorption by BIEs, consistent with electron–hole
separation and suppressed STE transfer. The spatial uniformity of
these signals confirms homogeneous Ag doping across single crystals.
These findings highlight the role of Ag interlayer dopants in governing
the BIE dynamics.